How do these guys do this? (Telemarket calls from a nearby suburb)

It seems weird to me that NoMoRobo doesn’t have something like that old Callwave app where you can set up your phone to forward calls to a special number, and then let them filter it that way. Instead, landlines are just not available unless they use VOIP.

If they did that, and the number was legit, you’ve lost the call. Doing it selectively is impossible, since the forwarding software resides in the telco switch, where NoMoRobo can’t get at it.
Simultaneous ring, which it uses, let’s it hang up the call if it is coming from a suspect number. So, no forwarding in the traditional sense - more cloning.
How it works.

Is there a reason why I’m suddenly getting almost a dozen calls a day now?

Before I would get maybe one a week of these scam energy company ads. Now I’m getting about 4 a day, at one point I got 13 in a single day, all by differently named “companies” but with almost exactly the same pitch of saving on energy costs.

This may be of interest.

You’re just lucky it hasn’t happened sooner!

Because you answer?

You’re one of the few live ones. Enough people filter by caller ID that the ones who don’t are obvious targets.