A quick trawl round a few websites shows trial flights in JP's, Yaks, a Vampire, Hunters et al. So it is definately possible, but how?
Just because it's being done doesn't mean it's legal. Quite often these are done under the pretense that it is cost sharing. However, as I understand it, you are only allowed to cost share the variable costs (fuel, oil, landing fee, etc), not the fixed costs (insurance, hangarage, maintenance, etc.).
I've just looked at the
Delta Jets website. It looks like they are selling you membership of a club.
Regards,
ifitaint...