There is a lot that can be deduced from this picture in Post 596, the only thing I do not know is the date. This makes some comments conjecture - which I will draw attention to.
Car 825 is seen here, in Pebble Mill Road I am sure either turning from it into Pershore Road or from Bristol Road. I believe it is the latter. The tram was built 1928/9 and was the last batch of trams built for the city (812 - 841). Just the two experimental lightweight cars (842/3) were built afterwards. They all survived until 1952 with the exception of 821 which came to grief on Breedon Bridge, Lifford on 26th. October, 1942. The car was unattended, the screw brake not applied, just the air brake which system leaked and allowed the tram to become a runaway, subsequently overturning on the curve. These cars were always based at Cotteridge depot.
Due to restrictions in the Selly Oak depot in the months prior to closure of the 36 Cotteridge, 70 Rednal, 71 Rubery and 72 Longbridge routes trams were stored on the outbound (Bristol Road to Pershore Road) track. This was controlled by lights as there was now only one track available. Cross overs were installed, with the attendant overhead wiring, at each on of the tracks in Pebble Mill Road.
The overhead wiring inspection being made might be simply routine or necessary maintenance. It could also be (conjecture) connected with the crossovers mentioned earlier in this post.
Now to the overhead maintenance vehicle AOH 7. This was one of five AEC Mercury vehicles purchased in 1935. AOH 7 and three others were scrapped in 1954 being surplus to requirements - the city no longer had trams or trolleybuses. The remaining two went to Walsall corporation who still operated trolleybuses until the WMPTE put the kibosh on them.