Thanks, but I obviously misphrased my question: is there a formal way of checking whether a given file is encoded for gapless playback without using Poweramp? After all, my problem is that Poweramp won't play these tracks gaplessly, so I wouldn't expect it to acknowledge that they're gapless. On the other hand, Windows Media Player will play them gaplessly, and as far as I can tell it isn't able to do that with files that aren't encoded for gapless playback - so I want some way of checking that I can reasonably trust.
EDIT: I have just done some tests and have found the following: if I rip tracks from a CD in wma format with Windows Media Player 12, they play gaplessly in Media Player but do not play gaplessly in Poweramp (and Poweramp does not say "gapless" in the audio info). I believe that these tracks are encoded for gapless playback on the grounds that they play gaplessly on Media Player and that the Wikipedia page for gapless playback says "Windows Media Audio encoded with Windows Media Player 9 can be gapless with Windows Media Player 9 and onwards". Therefore I conclude that Poweramp will not play (these) gapless wmas gaplessly. Is Poweramp really able to play gapless wmas without gaps?