Yes, from what I recall, the keeper said the Rusa were in the plantation that you can't see into. I think we've seen the Axis down by the bison for the last few years, mostly during our June visits.The Barasingha are also in the small seperate park around Paris House- you can see them by driving in the big stone gateway off the main road and up to Paris House which is a restaurant. I've been in there several times and never seen Rusa as well, but wasn't expecting them there. Part of the area is a dense plantation you can't see into from the driveway.
I've visited Woburn many times over several decades but never seen the Rusa or Axis there- though I haven't really looked for them before. Like so many places, finding out any information there that isn't just general fluff is always difficult...
We found it quite frustrating at the deer safari that they only really wanted to show us the red deer, when we were more interested in the less common species!