Yes

naw, doesn't seem like it.

I just spent an ungodly amount of time trying to find a bus in my ongoing save, including entering debug mode and spawning it in... it wasn't available to spawn. I started a new file to test it and make sure it was installed appropriately and bam, there it is plain as day, available to spawn.

idk if there's some way to make it work but nothing I could find online suggested it's possible. Seems like you have to start a new file.