The ownership of buses has changed over the years.With the upcoming closure and demolition of Perry Barr Garage and its replacement by a new building plus the future closure of Liverpool Street that will leave Acocks Green and Yardley Wood as the only traditional style garages still operational. These days open yards that cost less in rates have taken over.
E.g Birmingham city used to own and maintain their own fleet of buses and so required large garages to do so.
Since privatisation, fleet operators prefer to hire buses for a fixed term. Included with the hire charge comes maintenance. One of the companies that provides repair facilities is 'Carlyle'. Name sound familiar?