Well, they had two choices in front of them. Suck it up and partner, or suck it up and risk this situation.

Whilst I'm sure they'd have gotten a 1-year licensing agreement with Microsoft I can only guess it'd come with a steep price tag on. Plus they'd just been burnt by dealing with a third party. Plus (again, sorry), they need to have the Maps application being used by people worldwide to improve the quality. It doesn't get better with time, it gets better with users moaning.