There was a post on here from the '09 season where someone let the snake do all the incubation in the tub, but he added a lay box with sphagnum moss and monitored the humidity and temps very carefully.
I've been wondering about this too and how hard it would be to do. I've only got a single '09 female in a tank who's not even close to ready yet, but I have no doubt I'll switch to tubs sometime next year.
0.1 '09 Normal Ball Python - Sheva
1.0 Crested Gecko - Sol
1.0 SHTCTB Leopard Gecko - Paradox
1.0 Cockatiel - Mo (Mohawk)
0.1 Peachfaced Lovebird - Bean
0.2 Mischievous, long-haired cats - Moxxi and Azura
And 1.0 incredible, loving husband.