Take a look at this from back in 2009 when Apple were raising the possibility of sueing Palm over the original Pre being too close to their iPhone (according to them):

http://technologizer.com/2009/01/23/palm-responds-to-apple-i...

Of course this never happened, because to quote Palm at the time:

"Palm has a long history of innovation that is reflected in our products and robust patent portfolio, and we have long been recognized for our fundamental patents in the mobile space. If faced with legal action, we are confident that we have the tools necessary to defend ourselves."

Note that this statement was written well after the spin-off of Palmsource.

It's not difficult to ascertain that ACCESS/Palmsource very likely granted unconditional use of the patents to the existing Palm that sold those very patents to them, therefore giving it basically unfettered rights to defend itself against Apple in this scenario.

I think -- although I am not sure -- that you have to own a patent in order to sue for infringement, which -- if true -- puts a big hole in your argument.