You should check out those racks during the 'work week'- not so empty, IME. And if the rack is full, the driver has the discretion to refuse you service- and there is always the risk that the next bus will be full as well.

Also note that they frown on people locking their bikes to the racks- but they don't have a problem with you locking your wheel(s) to your frame.

And you're supposed to remove anything that could fall off while in transit- lights, water bottles, basically anything that isn't bolted or zip tied on- and they aren't gonna replace any of those should you not remove them (I lost a water bottle once). And any large bags should be removed as well, as they could potentially create blind spots for the driver, but this kinda depends on the driver's attitude and how the bikes sit in the driver's P.O.V.

I discovered early on that pannier(s) didn't work doing bike/bus because a) I never knew if there would be a dry spot for me to set the pannier(s) down on in order to load the bike and b) I never knew when I would have to hustle to another stop (whether on the same route or on a parallel route) and I didn't want to hold the bus up any longer than necessary, so I adopted a backpack in a crate to carry my stuff