To achieve this, we do vrf route leaking via static routes. It is not possible to leak directly between to vrfs, but it is possible between vrf and global in both directions.
VRF INTERNET (leak destination to global)
ip route vrf INTERNET 10.0.29.3 255.255.255.255 10.170.137.1 global
VRF ATT (leak source to global)
ip route vrf ATT 10.170.138.14 255.255.255.255 10.170.138.14 global
ip route 10.170.137.1 255.255.255.255 GigabitEthernet1/2
ip route 10.170.138.14 255.255.255.255 GigabitEthernet1/9