Unless the drains were clogged, why would there be any water
in them?

CY: The drains would only have waer, if they were horizontal
runs.

And
what little is left in the traps would have plenty of room
for expansion.

CY: I think I remember hearing of traps cracking. The ice
expands sideways.

What you need to do is shut off the main water supply valve,
and then drain
as much water as you can from the supply pipes by turning on
ALL the taps,
especially the one in the laundry sink (in the basement), if
there is a tap
down there.

CY: Yes, there is a laundry sink. I'm also concerned the
water pipes may have low spots or horizontal runs. Might not
be able to get there with my generator and compressor.

Why is the power off? Reasons beyond the owner's control, or
what?

CY: I'm not totally sure. the house is unoccupied, and
beyond that I'm not sure.