Only a PS3 icon is displayed on the PS3 XMB when the game is highlighted, and you don't even have the option to "copy" the game to PSP that is normally available for PSOne games saved on the console. Pocket Fighter doesn't even show up in the PlayStation Store when viewed on PSP.
It's not a control issue, since Pocket Fighter doesn't use any of the PlayStation shoulder buttons in gameplay, much less the two missing from the PSP. We're contacting Capcom to find out about this uncommon restriction.
[Update: Chris Kuspis from PSN Stores pointed out that Pocket Fighter isn't the first game with this restriction. Motor Toon Grand Prix and Delta Force: Urban Warfare are both PS3-only, as are several Japanese releases.]