I don't work on a FCP server, just with FCP and P2...I was just going by the definition of a server...I went to Apple's website, and realized I was SO wrong...Sorry....
After looking around, I don't know whether the P2 card could be seen as an asset...The transcoded files could be...My first inclination would be to do a full auto "log and capture" on the cards through FCP...I'd do some really busted down version that would transcode superfast and then put those clips up on the FCP server...After editing, you can Relink and transcode to ProRes or whatever for the final form...
Basically you'd be using two levels of server...The traditional "dummy" server which has the P2 cards in folders in network storage, and the FCP Server which uses the interface to help share transcoded files for everyone...
My money is that you'd have to put them all through log and transfer before they could be seen as assets on the server...Maybe it'll change in an upcoming version of the server...
To be honest though, I'm just shooting in the wind...