Jeff,
The PLANT_AREA, SERVICE, SYSTEM and UNIT all write to separate tables in the plant project database. The tables are named OPPID_AREA, OPPID_SERVICE, OPPID_SYSTEM and OPPID_UNIT. These tables will not exist in the database until AFTER the first sync.
The ability to delete these services was removed do to implications with relationships and links to components. This is being re-engineered by Bentley development.
In the interim, after verifying that a specific value is not used on any components, you can manaully delete these from the respective tables.
I hope this helps,
Tony DeRosa
Bentley Plant