Yes - I have thought about doing it because it is often too warm here where I live, and the refrigerator would be great for keeping them at a safe, steady temperature. I have too many tortoises though - I'd never get them all in there!!!!
I think a few members actually use old chest freezers or fridges to hibernate their tortoises, although I do not believe they are plugged in. I thought they just use them because of the insulation and they will keep a fairly constant tempature throughout hibernation.
I was going to buy a wine fridge to hibernate mine but I went with the natural option. The female emerged last week for a few days and went back under this week in the beautiful weather we have been having. No sign of the boys yet.