If it's a spare, svc 858 will be short of 1 bus. (According to
www.sgbuses.com/wiki)
I'm not sure which bus perms that slot without a perm bus, but
I'm 100% sure 134H is not a 858 permer since it did not get the WAB
stickers at teh windscreen and front doors, even though it is since
on 858 quite alot of times.