Rail runs on tight schedules and run from single point to single point, which leaves it un-utilized for long stretches between the train schedule. Trail is open full time for people looking to use it.

It's the same issue with the light rail over dedicated bus lanes or Bus Rapid Transit systems. Light rail is great until something disrupts the path from point to point. The buses allow for flexibility caused by disruptions.

I'm not sure why you're so dead caught on rail. It's pretty great for a lot of things, but there are plenty of other options and solutions that provide more flexibility and are less costly to achieve the ends. For a small spur like this I'd argue that it makes a lot more sense for it to be a pedestrian right-of-way rather than a rail.