Hi Karim,
Lets look at PP-PM integrated functionality:
1.In the case of Integration between PP module and PM module author used PP work center Capacity for maintenance operation demand stuffing (author inserted PP WoC as Maint.WoC in the EQ, PP WoC have been copied in the Maintenance Work Order Header and Operations). In that case "maintain system condition as not in operation" don't have any sense. And in my opinion it isn't quite correct from business side of view.
Operations (Production) and Maintenance it is two separate departments, with their own processes and work plans.
Production Planner should see planned Maintenance activities, as a "marker" to communicate with Maintenance Planner and plans synchronization, but not as obligatory rule. For that purpose "maintain system condition as not in operation" and PP WoC in the Location data of Maintenance Orders and EQ's are used. Only with that scheduling data Production Planner will see Maintenance activities as "marker" and not as demand.
2. When Production Planner will see Maintenance activities on the Planning Table, he should communicate with Maintenance to establish timeline for EQ shutdown.
3. Maintenance planner can manually shift maintenance orders to the planned EQ shutdown dates, or can use Revisions and Maintenance Event Builder functionality for rough cut planning.