If you are talking about the 7 in the Warrington Hex
Yes, that is the company.
then yes, it must lay a yellow tile as its first action.
That is not in the rules. While it might be stupid for the owner of the M7 to forgo laying a tile, there is no requirement to do so.
The question is, in the event the owner chooses not to lay the tile in Warrington, will an L train owned by the M7 run for revenue, or not?