A 7705 SAR that process BGP 3107 labels always re-marks the TC bits. Ingress classification is based on the received TC/DSCP bits to FC. Egress re-marking is based on the QoS queue policy.
A 7705 SAR that does not process labels on a BGP route tunnel such as a 7705 SAR acting as an LSR, does not re-mark the TC bits.