I did the same exact thing for ours when it got to -30s one year 

 Basement was probably around 65.  They did just fine overnight.  Getting them to adjust to going back outside the next day was a sort of slow process.
Now we use an oil filled radiant heater in the coop when it gets that cold and it will keep the coop at a decent temperature for them.  I would never hesitate to bring them inside again if needed, though.
Some people use a pop up tent to contain messes inside, I thought that was a good idea.