It would be easier just to build a wide tarmac busway on the same real estate.
Which would flood unless there was extensive drainage works, probably including some metalwork in the roadways, which the buses would drive over occasionally and damage, resulting in hazards to cyclists. The wider the tarmac, the more water to shift, the more drainage and it's the fens, so engineers frequently underestimate the amount of water needing shifting, which is part of why we have so much trouble with flash flooding on modern estates around here. Plus there would be constant political pressure to open it as a relief road for cars.
With the guided busway, everything between the wheel tracks is basically a drain and the buses never (well almost never

) drive onto it. If you're going to run buses across that stretch, the busway isn't a bad concept.