> Are there risks involved with that? Like for example, they could start playing games with you by saying 'sorry we're doing construction for a week, you can't access your office' ?

Probably? I've never written up a plan using an actual monopoly telco's CO, exactly for this reason. It's easier to find anywhere else to start from, and usually cheaper too.

I only mention it because my experience is mostly suburban / small city related, and I know the majority of small ISP / WISP guys are hyper-rural. They may not have any other options available to them.