This lab has two different ISP ASNs connecting to each other over a sub-interfaced link. This link has been placed into the customers VRF, which has been configured on both ASBRs. A standard IPv4 eBGP session has been created across the link to exchange routes. This method is commonly referred to as Option A.
A cheat sheet on the different MPLS options can be found here.
> GNS3: 10 x 3725s
> EVE-NG: 10 x IOS-XE 16.6.5s