It may not be a "new" posting, but a compliance with the new law. It has never been a requirement to post at the door. The requirement has always been to post the "no firearms" sign near the liquor license. From what I understand, Chipotle stores kept their liquor license in a back hallway.
This year, we (AzCDL) managed to get a change added in a liquor realted bill. The new law says that the liquor license must be posted in a conspicuous location. That brought the liquor license out of the back hallways.
As far as I knew, all Chipotle stores ban firearms. They're based in airy fairy anti-gun Colorado.
Fred