yes, Ancestry do their own (rumour has it in the middle east, or maybe it was the Philipines ? ), as do FindMyPast and the others on the market. All they get from the UK Archives is the microfilmed original pages.
I believe that the only 'shared' transcription is that of the 1881 census originally done by the Church of Latter Day Saints: Ancestry use this - hence why its the only 'free' Index, which they complement with the original enumerators pages ....