We just extracted BTG from a Segwit address for a client. It was hard to figure out at first, but relatively straight forward once we figured out our issues. The WS team member that did that job it will write it up soon so the community can benefit.
Any update on this? Would be interested to see the technical details behind extracting from SegWit addresses

We've been quite busy extracting BTG & BCH for clients & working on our automated digging website, which should launch in the next week or two.
When things settle down we'll post the step-by-step for SegWit.