NovaBrunswick
Canada Connoisseur
Speaking of Darkrai and Cresselia, I know it's not a bridge, but one of the caves in BW2 apparently leads back to Sinnoh. I think it's the one nearest to your house. The fact that the Lake Guardians (Uxie, Mesprit and Azelf) can be found and caught around Unova strengthens the Sinnoh link further. Could Sinnoh and Unova be geographically near to each other in the Pokémon world?