Are you running any kind of translation on the incoming CLI. I've known problems whereby incoming calls with unknown CLI are hitting Phones with Call forwards back to external numbers and the gateway rejects the call because the outgoing CLI from the CM is full of non-numeric Characters.
It could be you have the same problem, have a look at the call manager trace file and see if you can see the call hit call manager and how CM is trying to route the call and then what rejects it. Trace files can be a bit daunting at first but after 30 minutes of staring they become obvious.
You may want to take at look at Class Of Restriction lists "corlist" under the dial-peer, answer-address .T. So anything that has 1 or more digits in the Caller ID will be passed, Map this as a subset to the outgoing dial-peer cor. Not done this but it looks promising. This with the dial-peers I recon assumes an H.323 IOS Gateway not MGCP so probably rules out the VG200 unless you can fall back to H.323 See:
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.