The F/TR team uses more of a weighted matrix selection process - experience shooting in team matches, attendance @ 'international' events, performance at regional events, and perhaps most importantly, attendance & performance @ FCNC where said performance can be compared with other shooters on a known basis.
Not sure what all the specs are for the F/Open team... other than they try to have multiple team 'try-outs' scattered around the country in a manner similar to the Palma team - and now you have to 'pay' for the tryout.
I think both groups are working towards having 'development teams' for international events in between FCWC - get people who have shown significant interest and ability the chance to work within the teams and gain some more experience in a 'team' environment and with the 'international' aspect.