Haven't been down there for a while but the gate has been open every time I've been past. If you're coming from Buandik you'll be able to check that before trying Mathew Track.
If you're coming from Halls Gap it'll be faster to approach via Mathew Track in any case. Take Syphon Rd past the Vic Valley international airport to the east end of Matthew Track. The east half of Mathew Track is easier going than Jananginj Jawi track. The western end of Mathew Track used to have some big ruts and a couple of sand patches (a soft roader should get through I think) and would be nasty if wet.