Having slept on this, I'm not so sure anymore.  I do believe what I said was correct.  The trademark featured on that page was for the circle, square, triangle, X combination, the same way the trademark on their for PS2 or PS3 was for those letters in that funny font, in that order and not for the individual letters 'P', 'S', '2' in those fonts.  Like I said, that particular sequence of the symbols does feature prominently in alot of Sony marketing materials.

That said, it's hard to believe Sony created those symbols and put them all over their marketing materials and then failed to put any kind of legal moat around them.

One thing I've noticed anecdotally over the years is that it is rare to see the Sony symbols on unlicensed 3rd party controllers.  '1,2,3,4' used to be pretty standard but since about the advent of the x360, you see 'A,B,X,Y' all over.  Often even with the Xbox color scheme to them.  If Microsoft has any claim to those letter and button color combinations they certainly aren't out there trying to enfoce it.  Of course, that letter combination dates back to the SNES and has been featured on many Nintendo controllers since, right up to the current Switch controller.  I notice the letter combination has also been featured on the Onlive controller, the new Google Stadia controller, and the Steam controller.

So I think there is little doubt that A,B,X,Y are open for public use.  By contrast, the lack of similar buttons from other manufacturers does make one wonder if the Sony symbols are truly fair game. 

To check my anecdotal observation, I searched around Amazon for a bit just now and other than flagrant knock-off products (of which Amazon is chock full), the only controllers I could find that used anything close to the Sony symbols used mutations of them (eg. putting large dots at the vertices on each symbol).

In googling various controllers, I did find that the Ouya controller used the letters 'O,U,Y,A' with the O looking pretty much identical to Sony's circle (how could it not) but is colored differently.

To me, all of this suggests that either Sony owns an outright trademark on those symbols, or other manufacturers are sufficiently afraid Sony will come after them that they avoid the symbols irrespective of Sony's actual legal position.  Although, it's possible they do so for product differentiation (although if so, then why do they all use the same 'ABXY' scheme?)

In googling this topic more, I also found this little bit:

https://gamedev.stackexchange.com/questions/61181/can-i-use-playstation-...

which suggests:

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While the letter X is not copy protected, the specific cross used on the controller, along with the other shapes: , are trademarked. Using your own art to represent the buttons (as in your example image), should be OK under fair use, specifically nominative fair use. Where the qualifications for nominative fair use are one of the following situations:

• The product or service cannot be readily identified without using the trademark (e.g. trademark is descriptive of a person, place, or product attribute).
• The user only uses as much of the mark as is necessary for the identification (e.g. the words but not the font or symbol).
• The user does nothing to suggest sponsorship or endorsement by the trademark holder. This applies even if the nominative use is commercial, and the same test applies for metatags.

In this case, you're not trying to use the symbols as your own, but instead are directly referring to Sony's trademarked buttons, which likely falls under the first category.

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If I read that correctly, it's saying you are ok to use the symbols under 'fair use', so long as you are using them to depict Sony's controller buttons, as you might in a 'Controls' dialogue in a game.

However, that does leave open the question of whether you are ok to use them in an art pack that you post on the internet for anyone to download.  Since the icon is intended to depict a Playstation button, perhaps that is ok, although certainly the context has changed from using the icon directly to depict the button in a Playstation game.

Moreover, all the license supported by OGA are specifically broader than 'you can use this so long as you use it to depict a Sony Playstation controller button'.  Indeed, they all allow you to use a work however you please with only some restrictions on how you turn around and redistribute the work.

So, for example, if you took a Sony style X button from an icon pack on OGA and used it for a 'Self Destruct' button on the control panel for a space ship in wacky galaxy spanning, time defying adventure quest game that would be ok by the terms of the license presented on OGA.  In fact, that is exactly the kind of use case OGA seeks to encourage.  However, it's unlikely that use would constitute 'fair use' of Sony's trademarked symbol.

So tldr;

Those symbols are most likley well trademarked by Sony.

They are also most likely to fine to use on icons depicting controller buttons in a 'Controls' dialogue in a Playstation game.

They could cause legal or other licensing issues if used in any other context, including contexts explicitly allowed by the license supported on OGA.

Therefore, the specific Sony button icons (square, cross, circle, triangle) are probably not suitable for works hosted on OGA.

Full disclosure, I have two controller icon packs up there on OGA both of which include icons depicting the SONY symbols on them, so I do have a bone in this fight!  Unfortunately, looks like I am on the wrong side of my own arguments on this one!  :)