I looked through a variety of bus & tram books, and they came up with bus garages at:-
Acocks Green
Barford Street
Birchfield Road
Bournbrook (Dawlish Road)
Cotteridge
Coventry Road/Arthur Street
Harborne
Highgate Road
Hockley
Lea Hall
Liverpool Street
Miller Street
Moseley Road
Perry Barr
Quinton
Rosebery Street
Selly Oak
Tennant Street
Washwood Heath
Yardley Wood
Concerning some of the other posts on this thread:-
Post #10 - The photo of the 6 austerity buses at Yardley Wood Garage (Left-to-right #1437, 1440, 1375, 1403, 1376 & 1439) was taken on 1/11/44.
Posts #27 & 29 - Bus #1845 (HOV 845) was withdrawn in 1968. Adverts on BCT buses (some on brand-new buses) first appeared on 1/1/53. A London company - Frank Mason & Co. - won a 5-year contract to oversee all this, with BCT taking between 70 & 75% of all the revenue (which was expected to raise between £45k - £60k p.a.), and Mason's taking the rest. By 1953, BCT had a total deficiency of £722,107, so the adverts revenue was sorely needed; in spite of this, however, free passes for OAPs, and those on National Assistance, were introduced on 3/5/53.
Post #50 - The shot of the 4 trams in Witton Depot (left-to-right #377, 337, 152 & 340) was taken on 22/3/39.
Posts #58 & 59 - It would appear that the prototype 'Q' bus, AHX 63, did NOT have any kind of front door to keep the weather out. Lovely!
Post #79 - It is not obvious from the photo that AEC demonstrator 2211 MK had a front entrance, unlike the other one, 9 JML, which had a rear entrance. 9 JML was purchased by BCT in 1957 and withdrawn in 1969. There was, briefly, a 3rd AEC demonstrator, 159 JHX (a Regent 5), which was loaned to BCT in June 1956 and which worked mainly on the #14 route. Appearance-wise, it looked similar to 9 JML, but never carried BCT livery.