As far as I know, there are no Northern Ireland Rugby/Hockey teams so the situation is a bit different than the other sports.
Also technically a Northern Irish player doesn't need to switch to England/Scotland/Wales to be eligible for Great Britain, they just can't represent Ireland. Of course, this severely hampers that player's international experience since Great Britain only competes in Rugby/Hockey at the Olympics (or friendlies/smaller tournaments) so I doubt anyone would choose this route other than to stir controversy or they have no intention in competing internationally.