I doubt UPS will be allowed to operate all EU network on N-reg fleet. They can get away with some routes but surely not all of them. Long existence of Star Air is rather confirming this, let alone smaller feeders.
No doubt TNT value is brand, contracts and network and this has very little to do with TNT Airways as such. At the end of a day TNT Airways is rather small operation. So I see two scenarios based on a fact that 51% should be traceable to EU/EEC individuals: a) UPS will keep TNT Airways (could be rebranded as UPS Europe) through some artificial ownership structure and possibly even grow it at expense of Star Air, although I wouldn't bet this will remain Belgian AOC and LGG base, or b) they will shut TNT Airways and grow Star Air.
There is some value in EU airline apart from intra-EU network and that's a traffic rights to/from Asia and Africa.