I placed a 500 foot run of four number 6 USE conductors, an RG 8 direct burial coax that splits off at about 300 feet and up an 80 foot pole, and an empty run of 2 inch P&C Flex in the same trench. The P&C Flex went to the pole.
After about 15 years the sun had worked on the direct buried coax where it came up the pole. So, I put an idler pulley on the side of the pole with a lag bolt and pulled a run of LMR 400 with a four wheeler through the empty conduit.
Anyhow, I never even thought about any conflict between the two 120's in the same trench as the coax. It was all wrapped together.
Never any problem.