McD's serves ketchup by Red Gold and Golden State. 30 years ago, there was a tomato shortage and Heinz restricted shipments to McDonald's so that they could boost their more profitable retail supplies. McDonald's got ticked off and dropped them. Heinz has been trying to win them back ever since.
Probably some privately-owned franchises serve Heinz, though.
I never heard that Red Gold made the ketchup for McDonalds but I didn't work at the plant that made #10 can, bag and packet ketchup.