Here is a count of ridership on Route 1. I don't know why I can't find the full survey.
For what it's worth, I have taken the 1 twice, and on both times found the bus strangely empty, given that I was going to catch a Go train. But it has pretty good frequency, so it must have some ridership (this might not be good logic to apply to HSR, but I am assuming that Burlington Transit assigns resources according to some level of reason).
The 1 (and the 101) is the only Burlington route that serves Hamilton. I can't imagine it poaching a significant number of riders relative to HSR's entire ridership. I'd be curious about the specific number, too.