So long as you check the filesystems at boot time you should be fine even
if the machine goes off at the wrong moment. Ok you might lose a few blocks
that were being written at the time but nothing serious. I'd think a cron
job to do a halt at 30 minutes before the timeswitch would be fine. Also
remember that even if the uucp overruns under Linux the halt by cron
will occur happily mid phone call.(I do hope your modem drops when that
happens 8-))

Alan