Well, lagering would be no problem. I like to lager at 34 degrees, but it'd be fine at kegerator temps. Fermentation might be an issue, though. Most lager yeast ferment at 48-54 degrees or so. That's a bit warm for a kegerator, but if you don't mind that, you can ferment a lager in that range.
I like to ferment at 50 degrees for about 2 weeks, then rack to the secondary and slowly lower the temperature (5 degrees per day) until I'm at 34 degrees for about 8 weeks. If you don't mind changing the temperature of your kegerator, then you could do it in the same freezer.