The aim of both sims are so different.
For ATCO-sims it is the aim to get a lot of aircraft passing in little time, yet the sectors are not to big. Meaning that in the sim the average time you have an ACFT on FQ is about 10 min.
To link to sims together (which both cost a fortune) so they can work together for 10 mins and than only acting for 1 ACFT is not really worthwhile at least for the ATCO-sim.
And I don't think you will get any economic calculation to justify linking 2 of those sims.
As for info on sims. I know of 3 different facilities within our organisation. Two of them also bookable for other organisations.
The other way that ACFT-sims get a better ATC interface could be interesting, however a couple of good lectures with some ATCO's will pretty much give you a good picture.
Another reason why it is so nice to have FAM-flights and FAM-visits. The better we appreciate eachothers' job the better things will go.
So pilots feel free to go to an ATC-center and have a look but also try to be open for ATCO interest.
A good talk and show-around is mostly a big eye-opener.