Doing a MBA on the Companys expense can indeed be a very good career move. my advice woudl be to discuss what the plan for you is once yuor training have been completed. Sure that plan can and will probably change but only the fact that there is a plan is a good thing.
I know of one recent US case in which a person was offered a MBA training, had time off to complete the training and once the training was completed there was no position available in the Company for a person with that expertise. From the information that I have it seems likely that this was the plan from the start ie the MBA offer was in reallity a buy out. This of course assumes that you hold a contract or position that somehow prevents the Company from just saying goodbye.