It is case by case but even the LCCC announcer slagged them off for it once, something like "the ECB have decided that 4 overs is too much for Sajid Mahmood so he can't play today".If the ECB don't allow them to play in a T20 its crazy, as if they need a rest. The cricket calendar in this country is bonkers as well, just hope Rob Key sorts it out. International's shouldn't clash with the conclusion of tournament's. Vilas back tomorrow thankfully.
On the other had releasing Jimmy Anderson for finals day when he wasn't good enough to play T20 for England, so never played T20, always seemed to disrupt the team.