When did even the ready lanes stop accepting drivers license and birth certificate as a viable means of verifying status?

I have been communicating with an organization on behalf of a loved one and they are telling us that she only needs a valid drivers license and a birth certificate to cross over in to Mexico and back in to the US when transported by them. I have questioned the validity of that statement and they directed me to search Google. When I came back to them because I could not find evidence of what they were telling us they sent me a specific link and that government site also did not confirm what they are stating.

Any info on the topic is appreciated.