The man standing by the bus is either a driver, or an engineer foreman, by the riding boots which they would wear. Conductors would usually wear more normal footwear.
David is right, the divers were employed by the engineering department under Loftus George Wyndham-Shire, whilst conductors were traffic dept men under Orlando Cecil Power. The two had a BIG falling out just before WW1, which was never resolved even when Shire retired in 1940.
The bus is brand new in the photo, it hasn't even had the lifguard rails fitted between front & rear wheels.
The location isn't known to me, but it could be just before delivery from the Tilling Stevens factory in Maidstone, Kent. It certainly isn't the stables at Bearwood, or the 'motor garage' in Tennant St, Ladywood.