So, are you saying you have 10.1.0.0/16 as an entry? Or 10.1.1.0/24 and 10.1.2.0/24 etc etc
If you want to correlate "list reg" vs "network map ranges" to output "subnets in network map that have no phones on them" I figure you could just do a raw csv export of the network map from ASA and put your Excel hat on and do some vlookups.
Or, if you feel like being a little reckless, make a new network region like 123 that looks just like your main region as far as config goes.
Maybe wait till people go home, or don't, and make a bunch of entries in the map belong to that region 123 and list reg reg 123
Network region is done on the fly in CM - phones don't need to reboot to pick it up and you won't break anything in overnight if you flip a bunch of subnets to region 123 and right back to region 1
That might be an easier way to check. And then if you get to 10.1.101.0-10.1.110.255 having no phones, then get brazen and make 10.1.111.0-10.1.199.255 all in region 123 and check those.
That might even be quicker than using the vlookup.
I presume your intent is to remove those ranges at some point anyway, so if having 0 phones in them is the criteria, then making those ranges be in region 123 could be the label for you to know there's nothing in there. So you just run through your entries 1/2/10 at a time, as long as list reg reg 123 is blank, leave the network map entries there.