Hi Astrolady
If it makes you feel any better -
We had an incident where we were turning right onto a one-way street, behind another car. (Illegally) parked to the right next to a building site was a lorry, obstructing view. Whilst pulling out my husband checked to the left again for traffic, and as he looked forward the car in front had braked suddenly and we hit them. They had braked because a car appeared from behind the lorry driving the wrong way, and subsequently avoided hitting him.
To the insurers, my husband was considered at fault because he did not leave adequate distance, despite the exceptional circumstances. However we chased the car driver who was driving the wrong way - he drove off and didn't care about us contacting the police.
We made a statement and they said they would pursue him only because he was driving the wrong way down the street (reckless/dangerous driving). As the car in front swerved to avoid him and made no contact, he was not deemed to be involved in our own collision. They never have pressed any charges against him and this was last October.
I think it very unlikely the police will take action if you did not make contact with the bus and no damage occurred (e.g. he had to swerve and hit someone else in the process). I would give a statement if I were you, as requested, but I can't see it being pursued. Would it just be your word against his anyway?
Vulcan has a very valid point - it's always worth making extra observations and anticipating this sort of scenario, to avoid this in future.