GP likely means any 911 call automatically has geo tracing.

>The dispatcher's computer receives information from the telephone company about the physical address (for landlines) or geographic coordinates (for wireless) of the caller.

Wikipedia links https://propertyofthepeople.org/document-detail/?doc-id=2108... as proof that the E911 feature is used by the FBI to track phones.

Unfortunately, definitive capabilities and constraints of this kind of cellular technology is hard to come by.