Yes, the English construction has to change somewhat; "How used they..." is not a correct English construction. It would have to be changed to "How did they use to be able to live there," (don't know whether that's accepted; it's awkward but technically correct) or, better because more straightforward, "How were they able to live there?".
I've actually always wondered whether "how used they to" or "how did they used to" is more correct. I've always assumed that the latter was the colloquially adopted (but less correct) version while the former was a more correct but very out of date and formal sounding one. Do you have any references to back up your assertion? This would be a great mystery to solve!
I appears that I may have been mistaken, and it may be formally correct (see https://en.wikipedia.org/wiki/English_modal_verbs#Used_to) although "rarely" (ibid. but more like "never" imho) used. The only such phrase constructed without "did" that I ever remember hearing is "[someone] used not to." Regardless, should you wish to be understood in (even rather formal) English conversation, then unless you are a character from another century or galaxy in a Dr. Who episode, it would probably be best to avoid "How used they to..."? imho.