Hi Ibrahim,
THere are different solutions available for Inter-AS MPLS VPN. When the ISPs belong to different administration, it is common to see the use of "Inter-AS Option B" to provide VPN service to a customer with sites connected to different providers.
Below is the sample configuration for IOS-XE (and IOS):
http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/mp_l2_vpns/configuration/xe-3s/mp-l2-vpns-xe-3s-book/mp-inter-as-option-b.html
In any of those options, the class of service ideally depends on how the provider agrees to handle.
-Nagendra