The Waubra line shut in 1968 after the chaff mill that was its lifeline, burnt down (Oddly enough the person who owned the mill, also owned one in Kingston which burnt down on the same night). I think the line remained open to the racecourse, but only until 1970 when it was shut completly.
As for remains...
Not too sure about Racecourse, but:
Midas; a platform mound remains.
Pisgah; No idea.
Blowhard; Passenger platform remains.
Addington; Platform mound remains, a newish house has been built next to it.
Waubra; As previously mentioned the water tower is now gone. However a 53' turntable pit with central pivot, loco servicing pit, passenger and goods platform mounds remain and a large windmill lays on the ground close to the site of the water tower - this was used to pump water into the tower from a large hole in the ground which also still exists (be aware - its not fenced AFAIK and is not easy to spot).
Two roads have also utilised the alignment.
Waubra Junction Rd; although it doesn't actually run on the line, it does take you to the former rail crossing with what was once the main road between Ballarat and Creswick. The rails are still in the roadway here. The alignment has been used as an access road to the former station site, which is where Sulky loop is located.
Branchline Court; This runs off from Gillies Rd towards the racecourse on the alignment itself. This road is quite new (about a year old), and is for a new housing estate. I do not know whether this road goes to the racecourse proper though.