Sure they can file, but when the existing studies including those from Linux proponents show hundreds of likely violations, and not a lack of violations, what is their chance of winning?
I would not venture to guess. Some suggest that MS put up or shut up. But the same can be said for the commerical linux distributors... if the code base does not infringe any issued MS patents then go for PSJ..... Otherwise do the later.
LOL! That was your argument for SCO winning their fiasco as well.