I used to buy vehicles as part of my job and always requested a certain brand and spec. of tyre.
Some suppliers would try and argue that it wasnt possible or try and charge a premiium but I got what I wanted without exception and never once paid any extra.
Previously I had asked the vehicle manufacturers why they used a range of brands of tyres.
Their answer was that their buyers were obligated to buy from a selection of tyre suppliers and not just fit the well known brands.
Seems a dozen or so lorries would arrive at the factory from the tyre producer and when the brand on the production line was exhausted they were the next brand to be fitted.
Never thought to ask for a specific brand on my recent Golf it would have been an interesting exercise.
But when they need replacing will be with Michelins.