I have GV setup on OBi110 and Anveo setup on SP2 for E911. I do not have a DID (number) with Anveo. Irrespective of having an Anveo DID, along with Callcentric, Anveo shows a callback number to the E911 Operator that is unknown to you and unique to your "call", which allows for the e911 operator to call back in case of a hang up. That is how there E911 works and if you you find this unacceptable, you should shop for an alternative E911 Provider.
Callcentric and Anveo use of an alternative callback number offers certain advantages over the standard approach. For instance, if you have all incoming calls to you Home Number sent to voicemail or routed somewhere else during the 911 callback, your calls would not get to you and the Police will likely be dispatched to your home. I fail to see how Anveo (or Callcentric) approach will be confusing, since you can be reached on either your Home number of the unique Anveo number.
BTW, this issue has been discussed at length on this forum if you care to do some basic search.