Safegate provides runway incursion detection & alerting on their airport ighting control & A-SMGCS systems. They have it installed in Singapore and other airports.
From their website:
Safegate - Success Stories - Singapore Changi Airport
http://www.safegate.com/data/safegat...Binder1new.pdf
It uses induction loops / microwave barrier detection systems in addition to SMR / MLAT