Out of interest, is there any reason a council could not establish a new muni or buy out a local privately owned operator?
Is there any act of parliament or whatever against it?
There's no specific legislation preventing local authorities setting up bus services, or buying existing outfits. The problem lies in being able to demonstrate value for money to the council taxpayer. Existing municipals aren't usually difficult to defend, at least nowadays, but the capital investment for new buses and associated infrastructure is hard to justify, especially if First or Stagecoach are already running services. Government policy in the past did rather discriminate against the municipals, the theory being that the private sector could do a better job. It's a matter of opinion whether that's worked or not.
With deregulation here in Wiltshire our County Council fell over themselves to appoint a series of local private operators to run buses. The result, especially in the evenings and on the most rural services, was a tatty minibus belching black smoke and not accepting tickets from other contractors. The council were unconcerned by this, as none of their voters travelled by bus. Matters had to be taken more seriously when it was discovered that school buses were frequently defective to the point of being unsafe. Wiltshire Council now runs a small fleet of it's own buses on routes that are unprofitable for Big Bus PLC. Swindon Borough Council continues to operate Thamesdown Transport, mostly on urban services.
Wiltshire may be largely rural, but we're big enough to host our own 'Bus War'. We're treated to the sight of two buses (one First, one Faresaver) on each journey between Devizes and Bath, neither carrying enough passengers to pay for the diesel, let alone the driver's wages. The winning company will be the one prepared to lose the most money. Private enterprise at it's most ridiculous. God Bless Maggie. Meanwhile, most punters are mystified by the appearance of two buses at a time, and don't seem bothered as to which one they catch. I don't know if First and Faresaver accept each other's tickets, I haven't dared to buy a return since the war started.