The idea of having Ubaldo start is much more defensible than the idea of using him in extras last night.
The main benefit Ubaldo brings to the table (in theory, and in practice during the latter parts of the season) is his ability to pitch multiple innings. If he starts (like anyone starting in a do-or-die game), he gets put on a short leash and the amount of time he's in the game is based on how he's doing. If he's September-Ubaldo, he maybe gives you 5 or 6 innings, similar to what Tillman provided last night. If he's awful, then you yank him quick, and any hole he's dug for you, you have the bulk of the game to try and claw your way back.
In extras, there's nothing you can do if Early-Season-Ubaldo shows up. If he gives up a run, the O's have no opportunity to get those runs back. As such, I think it only makes sense to go to him if the game drags on and you need to get innings from someone.
There's just no way, particularly given the volatility of his season, that Ubaldo should even come close to entering that game with Britton available.