I asked about this at the booth at York last fall. I have a unit that failed that I would not consider a warranty issue(it was probably past the year, and also I had what I think was a lightning strike near my house that also fried an answering machine and modem at the same time). At that time there were no boards available either (didn't even show up as a part number then, so maybe there has been some progress).
Hopefully they will be able to make this available someday, though I wouldn't be surprised if it's like an engine shell or body of a freight car, you may have to exchange the dead/defective one.
I can see if they don't want to just offer the boards for unrestricted sale, since then lots of people would be upgrading older non-TMCC switches with the boards (and thereby cutting into the market for the full unit significantly), but they really need to have them available at some level.
In my case, the unit that dies still functions perfectly as a remote control switch, so there's no way I will be throwing it in the trash just to make a statement.
-Dave