As this topic was touched anyway....
"How is the service provided by XYZ is paid by the parties entitled to dispose? OR
Can/Does ewm track the data of warehouse transactions per party & time for which respective stock was stored in the warehouse, to link it with calculation of service fee payable by the parties? "
With EWM9.3 the new feature of warehouse billing is available, so this answers this question with yes.
Warehouse Billing - What's New in SAP Extended Warehouse Management 9.3 - SAP Library
Best regards
Juergen