Hi
Best thing to do if you want is to have the UPS going, but do a manual power down and up of the router in that time, you'll thank me.
Well it depends on what they are already sync'ing at, for me on 80/20 I couldn't get any more speed when we had an area wide power cut and so I was likely the only person connected, but SNR went up by around 10db during the power cut, so that is what cross talk is costing me.
Depending on the amount of cross talk, re-syncing during a large area power cut may get you a lot more speed, but it's only going to be short lived, as once power is back on and cross talk returns, any large gains in SNR will go causing the modem to drop and resync.
Regards
Phil