A couple of people are reporting success with the restore feature. Here is one success story. I don't have my iPad with me at work. Any brave souls out there want to test this out to see if it works?
EDIT: one user reported that he restored, got his old city back, closed the game and when he restarted he was back to a new game. So this whole thing seems to be yet another GI crapshoot!
"Restart the game, the restore window should automatically pop up. Scroll to the right until you find your last level before the crash. Should take a few seconds, but my city reappeared. Just don't touch the links for the building sales on the right!!!! It will crash and start over again!"
"If you are using an iPad, try closing from multitask bar then turn off and back on iPad. I did that now back to my old game. But yeah when do we get the 50 city credits and other useful game items"