Fact tables are based on measurable quantitative attributes surrounding business entities, usually processes. If the business process crosses normal departmental boundaries, then so be it. If it crosses transactional system boundaries, then so be it.
For example, Purchasing may have several systems (requisition, vendor management, receiving, inventory) and cross departmental boundaries (purchasing, accounting, warehouse, etc).
In your case, the fact table processes are Service Request and Order Fulfillment (pardon me for putting words in your mouth - use your business terminology).
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