I have found the following reference
"The Canadian, British and Indian Armies all used Foxes operationally although it was never particularly popular with it's crews. Canadian Foxes were relegated to the training role in mid 1943. India kept her Foxes in service into the early 1950s."
http://users.bigpond.net.au/blitz_trucks/CANCARS.html
Digging around I found references in a history of Canadian HQ to the Canadian forces during WW2 relinquishing orders for Lynx armoured cars to allow them to go to India in response to a request from Britain. Humbers are also mentioned - one wonders if some Foxes replaced these latter, especially as it seems that some units appear to have been replacing theirs with other vehicles about this time.
Given that Lahore is in Pakistan (well within) I suspect that the Fox found in India may not have come from 7th Royal Tank Regiment.
The mechanisation of Indian Cavalry regiments from 1939 onwards was predicated on the assumption that Indian mechanised units would increasingly replace British ones in India. By 1947 there should have been relatively few British armoured car units in India, however the problems (understatement) of partition may have caused some rethink.
Does anybody know what is the formation to which badge on the Fox in the photo in this thread belongs?