Scenario: who places the dental implant abutment when there is a specialist and a restorative dentist at a different location (have healing cap on)?

Either, but...: Preferably, the restorative dentist or prosthodontist will select and place the abutment (or make a custom abutment) for the best esthetic and restorative result. If the restorative dentist has limited experience in implant restoration, he may ask the surgeon to place a prefabricated abutment.

Restorative dentist: Many times a specialist or surgeon will supply the abutment to the restorative dentist. When this is the case many times it works out fine but sometimes it does not. The restorative dentist is the one who places the abutment and has the insight to know which abutment will work best. Restorative dentist and surgeon (implant placer) must work closely together to make sure the case works as planned.