Buses can be used by the public,its not a public place,its a privately owned vehicle with a lot of rules and regs to follow when you pay for the right to travel.Thats why inspectors can fine fare dodgers,or get undesireables removed.And a bus can go out of sevice and refuse travel to anyone not wanted on the bus.because it isnt a public vehicle,its a private vehicle offering a sevice in exchange for money.
Ill leave that to you,when you have a secretly recorded witness

.Just curious,but all this help you want to give to the public,when are you going to tackle anti social gangs on the streets,i mean they are as easily found,normally in the same area upsetting the locals?And as you have pointed out on a number of accasions,you can handle yourself,so it shouldnt worry you should it?
And secretly recording a conversation is dishonest,doesnt matter how you butter it up.