Maybe as someone suggested earlier there are exceptions up to a higher limit if the players involved are U21? I remember the Rangers Newcastle dealings as well. Rather than performance I think that was all about Ashley reducing the wage bill at his big club and ripping of Rangers at the same time.
Otherewise I'm sure Mark McGhee would have losded our team with top players from Bayern Munich and other German clubs.
The rule is simply that you can only loan 1 player from any one club in the same league I think i.e. we couldn’t loan another Hearts player, but can loan a Celtic player. Well I think so.