EC and EIC trains should have them. TLK trains, probably not. If second class on an EIC train between Warsaw and Poznań has outlets (the newer coaches, at least), then I am inclined to believe that first class would have them as well.

I am boarding a TLK train to Częstochowa on Sunday (which goes onward to Wrocław), so I can probably check to see if what I'm saying is necessarily correct.