Mitchelli and tigris on South Mountain have the most obvious opportunity to "cross paths" and hybridize. But they don't. There is something else keeping them from doing so.
Rattlesnakes have split into their distinct groups for a reason, and many species can cohabitate the same areas because they are so distinct, not because they can hybridize. Hybridization may still occur, maybe as often as other weird things occur, like aberrancies. But if all it took was the crossing of paths, we wouldn't have so many distict species co-existing.