Until recently, buses could only compete (under the Transport Act 85) but only in the last week (under new regulations) competing bus services have been allowed to co-operate allowing a return ticket issued by one company to be used on the other company's buses.
I'm not sure that the Transport Act you mention prohibited such co-operation. For instance, there have been numerous "joint service" examples of return tickets issued by one company being valid on another company's buses over the years since in my part of the world.
I found that quote
very interesting too, CLPG. Whilst it's true that there are the cooperative elements mentioned by Lee, there are all too many cases where I've had folks (including the owner / MD of a bus company) tell me that he can't work with another company for the common good of the passengers because of the various rules governing buses.
I suspect there are elements of truth in limitations that have been placed, and also that the laws / rules / limitations are (or have been) used as a very conveneint excuse for taking an approach which is competitive between operators to the detriment of the good of the passengers (and then ultimately to the number of passengers and the income of all operators on a route).
Where do I find more about the amended regulations, what's changed, and what the changes mean? Could they also have implications in syncronysing trains to buses too?