tatfiend: Some Incline bikes seem to be offered on-line these days here:
http://webbicycle.netpaths.net/bikes/
The model I got, Cruz7, is only offered there in one size now, 15". I have no idea if they're legit, I bought mine elsewhere. I've sent a couple of emails to webbicycle and got no reply. There may be no future to this company (and many others these days, including GM!), but I figured somebody's gotta use this bike while it works, and if and when the shaft drive wears out, if I cannot get a replacement, then the wheels, tires, and the Nexus hub and other parts are transferable and worth most of what I paid for the bike.

Is it possible to buy a replacement shaft-drive unit now, to make sure I have it for later? Where? Would the drive sold for the Dynamic brand fit the Incline? (How many different models does Sussex make?)

Hmmm, that site has an "exploded" diagram of the shaft drive, here:
http://webbicycle.netpaths.net/technology.php
and it looks like the BB is integral to it, i.e., the bike frame only provides a cylindrical space for it but the axle is held by the shaft drive housing that's inside that space. That diagram should be useful, although I still don't see how to get that left side plate off safely. Can hammer the right end of the axle but that may damage the bearings. Perhaps the left side plate would come off more easily?