A few years ago I was working on the foundation of my house and the project went on too long - the excavator disappeared and it was a mess. Anyway, it was January and I had the incoming water line exposed outside the foundation. It froze once in January and I had to thaw it but it gave me no other issues.
In your case, I would see if you can run heat tape off an extension cord from your unit and put that on the pipe. It'll add a few bucks to the bill but give you the peace of mind that it's being taken care of.
I dunno... running a heat tape into someone else's unit could open you up to liability if it froze up or caught fire. Force the owner's hands, even if the owner is a bank.
Many condo associations where intermittent occupancy have a minimum temperature rule built into the bylaws for exactly these kinds of reasons. (eg. My MIL has place in Maine with a 50F min-temp rule that's primarily her summer place. In January only about half the units are occupied, but in July it's full-up.)