If both beers are identical it would probably work okay. They would need the same gravity, level of disolved O2 and pitch rates. Or at least very close.
I have two beers in my ferm chamber now, one a barley wine and one a low gravity ale. I pitched a yeast cake in the barley wine and a single tube of yeast in the basil ale. now, after three days they are the same temp but for the first two days or so the BW was almost 10 degrees warmer than the basil ale. I 'control' my temps with a cheap-o timer but had I had a single controler either the BW would be too warm (if I was monitoring the basil) or the basil would have been to cool (if i was monitoring the BW)