It looks aftermarket, and handcrafted so I cannot even guess.

If you want look in the kick panel you may find it again.
If so it may lead you to a module, or to the radio area, or dead end anywhere.

 

alright, I'll pull the tire out this weekend an find the source, thanks!

 

Mine had strobe lights installed in the tail lights. The wire is in a 3 wire pair very similar to your but mind had been cut. Just a thought not sure is yours.

 

Mine had strobe lights installed in the tail lights. The wire is in a 3 wire pair very similar to your but mind had been cut. Just a thought not sure is yours.

Just a FYI.
The two cables are not very similar.
OP's cable has a smooth jacket and shows no indication of having a fourth wire or shield.
@roadrunner00's cable has a bulging jacket and foil shielding is visible.

Strobe lights use high voltage. Usually over 300 volts for the light output and over 4000 volts to trigger the flash.
This usually results in radio interference, especially with two way radios that receive relatively low power signals.
The strobe cables should be shielded to reduce this.

From the size of the wire and connector, the limited amount of cable length, and the age of the car my guess would be that it is for a cell phone.

Second guess would be it is part of a factory Bose sound system or aftermarket amp.

I would expect to find other cables if this is correct. Heavy power cables and other wiring.
Extra screw holes in the rear deck or back seat supports would be other signs of aftermarket work.

There is always the possibility of a car alarm.

Modern emergency vehicle now uses LED lighting (low power) and digital communication (better reception in most cases).

 

That is definitely part of the emergency lights/systems from the typical controller added to 9C1's. I own a 94 9C1 that, after some time, became very troublesome due to the many haphazardly cut cables and wires when the police dept, mechanic removed their equipment. why disconnect everything when cutting is so much quicker? I had random events at any given time with head and park lights suddenly going into emergency flashing mode. When I finally found and removed the controller under the dash there must have been an extra 50 ft, or more, of that gray cable-like harness. Total removal was the only option I had to fix what they f'd up.

 

That is definitely part of the emergency lights/systems from the typical controller added to 9C1's. I own a 94 9C1

As @roadrunner00 and others has found any vehicle can be outfitted with emergency warning lighting.

@BearCaprice has a 1991 Caprice Classic Limited with keyless entry.(possibly power antenna)
He has been working on the rear light harness and has not commented on any extra wires in this area.

In most cases in Canada the 9C1 ( or other OEM equivalent) would be ordered at a federal, provincial, or large city level.
Most municipalities and small towns used the federal RCMP.

Anything is possible but the probability of a non SEO car having service equipment is low.

One of our Prime Ministers used Roadmasters instead of Cadillacs for his official government use.