I'd wager that the local cold-tolerant species is non-active, just for the simple fact that there's no record of their usage in that way. Plants often use alkaloids as defense mechanisms. It's possible that they have the same alkaloids, different less-active ones, or none at all. Its possible they had actives once upon a time but lost them due to lack of needing them in cold environments. It's really anyone's guess. I'd bet they CAN be crossed since their growth style is so similar. They just seem compatible. Interspecific breeding is relatively common, and inter-genus crossing isn't uncommon.
Only one way to find out! I may give it a shot myself once my capensis seeds get here. I'll be sending some to you as well as per our previous discussions. I'm excited to see what we find.