It looks, we have a little different habits/standards here.

In my company it happens quite often, that the service engineer specialized in Linde must deal with the truck of different brand.
It usually happens, when the customers fleet consists of some amount of "our" machines and few other.

The customer expects, that the guy we delegate for him will solve ALL his problems (we have the "one face to the customer" philosophy).
This is the service provider obligation to ensure that his specialists are able to deal with the trucks they have in their location. When they are different brands, this is still his headache.
We must provide the training, the documentation, technical support, spare parts logistics etc.
Otherwise, the customer will be unhappy ;-)

That's why it's a bit hard to understand for me, why the different guys from different locations must come to the customer to service sometimes similar trucks (like Yale and Hyster).
Such situation is very uncomfortable for the trucks user, while he cannot estimate his monthly/yearly maintenance costs, TOA (truck out of action) factor etc.

I think, the issue (and the key to the success in this branch) is, that if the customer makes, let's say, shoes, let him make his shoes and not bother with his tools (like hammers, computers or trucks).
We, the service companies, are the ones, who take care of these tools, and our job must be presumable, clear, economically reasonable, and less bothering for the customer, the better.
Howgh ;-)