What would stop a local randonneur club from organizing a 1200K from Boston to Montreal and back? The roads are open to the public and the route could be modified a bit so it wasn't a 100% copy.
Probably the same thing that keeps most randoneering clubs together -- personal connections and goodwill. Jennifer Wise, both as one of the founding members of RUSA and as one of the local fixtures in the New England randoneering scene, has earned a lot of local respect. Along with Johnny Bertrand, she's done a lot to get randoneering going in the States, and has been especially key in building the New England club.
As I said, I was kind of surprised to hear that the interruption of BMB was due to the fact that it's in search of a buyer. What I heard was that none of the local organizers had the resources to take it on, and I interpreted that as staff/volunteers, instead of money. There's a bit of chatter going on in the New England Randoneering list about alternatives to BMB, but none of it has really caught traction.