I remember a job i did with a solar power company where we did a similar thing.
We build a 30kw solar grid 400ft from the nearest building, and ran 440v stranded copper (2 x 000 gauge) along side a shielded cat6 and I get full bandwidth speeds most of the time. We ran 23 gauge solid core shielded cat6.
Keep in mind that it is not necessarily the voltage that creates the interference, it's the amps. we do not get full network throughput (about 2/3 total speed when peak power usage is traveling the power line) even with the highest end shielded cat6 we could find, but we have a 400ft run, and significantly more amps than your scenario it seems (I do not necessarily want to assume).
I think you will be fine with network speeds if you go with nothing less than shielded cat5.
We did not have any inspection issues doing this (I would recommend making sure for your area). cat5/6 is considered low voltage, and is not restricted to be ran along side a high amp power line for my project in it's location.