Wierd. All the literature mentions they usually fail closed. Perhaps thats old information? I'll go with real world experience any day though.
So maybe I run a few MOVs across the 3 phases and call it good? Of course, MOVs have their own problems...
Unfortunately, my budget isn't Opto, it's HongKongSpecial. 
Hopefully in two years I can pull this out and put an Opto in.