This is actually partially true. If you call Bucks 911 to report an incident on I-95, they will first inquire if fire or paramedic services are needed, and will 'patch' the call to PSP Trevose (and they will generally remain on the line to listen). PSP Trevose will then dispatch their patrol cars.
If there is not a need for fire or ems, there will not be any routine notification to any Bucks local police departments.
However, if fire or ems is requested, the standard protocol in Bucks is for the local police units to be advised that fire or ems is responding to a report of x on I-95. At times, if the local department has a unit available, they will head up onto I-95.
So for a crash or fire, the local police will be advised and might respond, but for a disabled, a DUI, a reckless driver, etc., on I-95, they are not advised.