Good news! The American webhost managed to supply me with MySQL dumps of my website's three databases (Bowjamesbow, Clarksbury and TransitToronto) and by a painstaking line-by-line import, I've successfully restored the operation of Transit Toronto's Movable Type back end. So, all of the data is now back up on 1and1's servers.
The final changes of the DNS system, to point all domains to the 1and1 servers are still going through. Transit Toronto, being an odd third-level domain purchased during the last days before the .ca domain name was reorganized (nobody purchases yourdomain.yourcity.prov.ca anymore, but I like transit.toronto.on.ca), is taking a little longer to percolate through the system. Once it's done, however, and the American webhost is sure that nobody, nowhere can activate the files on my system and kill their servers again, they will reopen my site for FTP access, and I can grab the Gigabyte of images and HTML files.
Can you believe that they initially wanted to charge me $150 to reactivate my hosting in order to grab my files? Fortunately, some people in the tech support department have gone to bat for me to help me extricate myself from this mess, and it probably helped that I stayed relatively calm when I asked if there was some way around the charge. I will make a note of that. This American webhost isn't irredeemable, at least.
If all goes well, normal operation could resume as early as this Wednesday evening, but it could be as late as Thursday afternoon if glitches rematerialize. I still have to painstakingly restore the databases for the Bowjamesbow and Clarksbury sites.