I would like to see if there is an answer for this as well. Along with possibly setting rights per subscription schedule on a single site. We are running into a situation where we have numerous subscriptions and they take a while to process.
Unfortunately, the ability to set different subscription schedules for different Tableau Server Sites is currently not built into the product. As a result, there is currently no way to prevent users from seeing all schedules run by Tableau Server. Users will have to simply choose the best schedule for them.
Hope this helps,
Please submit your feature ideas to the ideas forum so others can vote it up as well.