There is nothing to believe, it is a simple fact. Corporate contract with CX from Belgium would provide limo transfer from CDG to anywhere in belgium for J. I used that double digit number of time and it was in my contracts.
I dont know if they still do it as I now live in Vietnam but I guess they do.
There is a cost to a limo transfer to CDG (AMS was also available) but it is cheaper than losing customers to Etihad and the few others who are flying to and from Brussels. That's the logic behind the system here.