AIR VBS on 6090 kHz - testing on simulcast mode ?

AIR VBS noted on 6090 kHz since check in on 9th April, 0900- 1200 UTC,  probably testing in 'simulcast' mode, // to AIR VBS DRM on 6100. During Dec 2009 tests were noted on AM 6090 150 kW + DRM 6100 kHz 50 kW.