Perhaps creating a Business as Usual (BAU) Project and using the PSI to take the task info from Service Manager (7?) and populate the tasks.
To do this you would need SM to have duration, effort estimates (and actuals would be desirable) and a resource/task key field shared by PS and SM. That way each task could populate the BAU project and have the assignees effort estimates affect other projects resource availability.
The frequency the BAU project must be updated.
Are resources Proposed or committed?
Task ID synchronisation between systems
Generic Resources, RBS and Team setups in both systems will be niggly
Task Approvals and workflows may well collide (this is very prob)
I would think more about producing an SSRS exception report for project and line managers to show resources with conflicts and over utilisation due to BAU and project commitments.