The tech priest dominus and cawl can do it already, so I think it's probably fine if an enginseer did it.
Though I can also see the fictional justification that the enginseer doesn't have the medical knowledge to deal with any possible injury to the human part. EDIT: Nope, I'm wrong about that. From the codex: "While other Tech-Priests concern themselves with the Quest for Knowledge, Enginseers take on a more utilitarian role, tending the servitor flocks and acting as custodians to the machines they serve." They should probably be able to repair everything from a fiction perspective.
Rules text for the three repair abilities if anyone needs to see how they differ:
Automatically Appended Next Post: I'm not a tournament player but I find a unit of Kataphrons with heavy grav to be a great escort for a tech-priest dominus. The reroll 1s and repairs he provides really help them. Though I'm sure from a competitive perspective the same points spent on something else as an escort for the tech-priest dominus is probably more efficient. I don't play or list build with that concern though.