Yes we have in Denmark.
We have been connecting: VBS3, SB and JCATS through DIS.
It has only been done for test and proof of concept.
We have done it for some years now, with various results.
The first times we had some trouble with the Calytrix gateway (and SB) that connects SB to the DIS cloud.
But a lot of those issues has been taken care of during the last year.
In the end it pretty much comes down to doing the hard work of getting all the DIS enumerations right.
I think it can be used to show the infantry guys what kind of support they can expect from tanks, IFV etc.
As well as train the different branches to corporate.
By the way I know that the Austrian army has done some similar things with VBS3 and SB.