Your local authorities on these matters should always be consulted to see if there are rules covering this situation.
Back when I was an electrician the rules in my part of the world expressly forbade installing power and any kind of communications cable in the same conduit/duct. If placed in the same underground trench there had to be a minimum separation, but I don't recall what that distance was. The purpose was to try to eliminate the chance of mains power being fed into the comms cables in case someone did something stupid, like put a shovel into them. The Phone company (we only had one back then) had similar rules.
From the network side I would advise against it because shielded or not there is still a reasonable chance of inducing spikes into the cable. While that should never be damaging it can certainly affect throughput. The shield is supposed to prevent that from happening but cable shields are seldom completely effective.