Yes, the quarry has been tarted up, and will feature on the walk this Saturday, as well as the barracks/gunsite.
It's actually an Anti-Aircraft gunsite, and although it did have an attached barracks, those have long since disappeared under an embankment. The gun positions and associated magazines are all still intact to some degree.
Not much I can add that isn't in the Secret Scotland site - the architects in charge of tidying up the gunsite recently posted on there looking for info too.
Been wandering around there since I was a youngster, although I'm from Westburn/Halfway myself, not Blantyre. I believe an alternative name for the area is The Whins, although it's more commonly referred to as Blantyreferme AA Gunsite.
Edited to add: There's a wee bit about it on here in this 6 year old thread:viewtopic.php?f=15&t=13
And you'll also find references to it in the Caldervale/Fin Me Oot thread here:viewtopic.php?f=3&t=1936