Until I deleted the URL within the window of the Auto Provisioning > OBiTalk Provisioning > ConfigURL, I could use OBITALK to provision GoogleVoice.
That URL is now gone from the dialogue window whether the Default option is checked or unchecked. (thanks to my excess fiddling). A factory reset (paper clip method) does not put the URL back in the dialogue window.
I'm expecting to want to use OBITALK to provision something. But, unusually cautious a couple of days back, I recorded all the GoogleVoice settings. So, it works again with my direct entry of the settings.
tftp://$dhcpopt66/$MAC.xml was in the documentation PDF and I'll give that a whirl. Oops ... doesn't stick.
Any confirmation or advice is welcome. Maybe a firmware reload?