Do a cool little test, call the RTA tech, get the answer, hang up, call them back, ask them the same thing.
Do this 5 times... You'll find you have 5 different answers.
If there was an engineers cert listed it should have the number on the rego papers. I know mine used to on the R33, and on the Supra.
If they're not listed, then the RTA won't have any clue of an engineers cert.
If it does already have one listed, then ask the RTA for it, as it's still valid.