used to/ was/ was used to

[riglos]

Could you give me a hand with this? I would really appreciate it.
What is the difference between these sentences?:
1- Boeing was in the train business.
2- Boeing used to be in the train business.
3- Boeing was/is used to being in the train business.*
* I'm almost sure that the last one is not correct, but why?
Which are the uses of "used to" as compared to "is/was used to" and "was"?

I think that in this case we use "used to" rather than was, because we want to emphasize the fact that the action is no longer true, that something has changed. We are focusing more on the fact that Boeing is no longer in the train business than on a habit in the past. If not, what are the uses and meaning of "used to"?

Thanks in advance!

Mara.