This won't be the response you want, but as someone who has worked in support: The goal is to provide sufficiently good service to as many customers as possible with as small and low paid a staff as possible. Thus, requiring the staff to be able to use a greater variety of software would cost more, because people with more skills are more expensive and because supporting more variations allows for a broader scope of possible situations and a larger number of possible problems to solve. It is not about FLOSS, it is just about constraining the tasks.
In addition to what helps a specific customer, the standard software may do things which are not obvious, such as searching an existing database for similar symptoms or recording the interaction or pulling information about the configuration in order to allow better diagnosis. So, the time to discuss what set of software is used is when you are subscribing to the support service. The contract could specify what they provide to you. Whether you have that choice depends on how that support came to be purchased. Mary-Anne
