According to what I have found, mostly from descriptions attached to photos posted on assorted websites, EDG is operating the oil run on Mondays and Tuesdays for SBB Cargo (SBBC).
They are also contracted to provide services for other operators, including Austrian LTE for the Swiss segment of their routes. This operation has included the delivery of Polish sugar to the Frauenfeld area. I don't know if this is a standing partnership or was contracted on a per run or per route basis.
It would be interesting to find out if there are new runs where these locomotives are in regular use.