Gordon S. Hlavenka wrote
All I really want is to retain control of these numbers, at minimal
> cost. I don't need them to physically terminate anywhere -- in fact I
> didn't plan to even use the Vonage TA, I'd just have them
> simultaneously ring to my cellphone.
Back in the time when AT&T was "the Bell System", you could do exactly that; retain control of a non-working number that you previously "owned" simply by paying a small monthly fee. For all practical purposes, it simply was a non-working number except that it was blocked from being re-assigned as long as you paid the fee.
Alas, I don't remember the name for said service. Maybe they don't even do that anymore.