"Fly Runway Track" means exactly that, you are required to follow the Track of the extended Runway centre-line. As noted earlier, this particularly applies in Australia, but is by no means limited to that country.
Similarly, "Fly Runway Heading" means exactly that, you are required to follow the Heading of the Runway direction.
If you do not have the equipment to enable you to fly Track, your response to ATC should be "Unable to comply", their separation standards are based upon it.
Regards,
Old Smokey