Is there a CLI front-end to the Contacts.app (formerly Address Book.app) database?
mycontacts --email '*@google.com' # to get Googlers
Contacts still has AppleScript support. You can see documentation for the supported properties and commands by opening its dictionary in AppleScript Editor.
I didn't find a way to check the actual email fields using a single specifier.
The closest thing to a generic solution is Shane Celis's
There are other options that may also work for you. Contacts just stores info in a sqlite database so you can access it with the sqlite command. You could create a custom script to accomplish a particular task if you want.
Scott Stevenson had a tool called abtool up that was popular for a while, but it appears to be a dead link now. You might also try searching through some of the stuff on GitHub. In particular, since Shane Celis's app appears unmaintained (while still functioning well), there are some who are building replacements.