Safe to use 220V electric clothes dryer when building has been bridged down to 110V?
It won't work.  Your 220V (really probably 240) outlets will actually have 0V, not 110V.  

The reason for this is that normally the 220V outlets make their 220 by taking both 110 lines that are out of phase with each other, such that while 1 is at +110, the other is at -110 for a difference of 220.  Since the power company bridged one of the 110 lines to make up for the dead one, that won't work -- they'll both be at +110 or -110 at the same time, for a difference of 0.