SYMPTOM
When using the Project Merge Wizard to merge one project into another, the subscriptions of the source project are lost in the merge while the subscriptions of the destination project are kept.
CAUSE
This is a known limitation of the Project Merge Wizard as you’ll see in the menu when selecting objects to migrate over, subscriptions are not included.

ACTION
Currently, the only way to migrate subscriptions is through Project Duplication. This issue is still being reviewed for feasibility by our Technology team although it is not scoped for any upcoming scheduled Strategy release.
WORKAROUND
Unfortunately, the subscriptions from the source project will need to be recreated through Developer or Command Manager. The source project should be the project with the least amount of subscriptions in order to reduce the number lost/recreated.
Article Reference Number: KB441991