Interestingly, it looks like video calling between the Apple and Android Skype consumer mobile clients and Skype for Business desktop client on windows (MSI and Click to Run) now works.
This is testing on a recent Office 2016 C2R Skype for Business Windows Client video calling Skype consumer on iOS
This is testing on a recent Office 2016 MSI SfB Client video calling Skype consumer on Android (thanks @VikJaswal)
The Windows Phone Skype consumer mobile client didn’t work for video in my test.
Previously this didn’t work. It’s not made the TechNet supportability matrix, so I’d assume it’s early days/your mileage may vary.