They can all play together, it just that only battle brothers can share buffs and transports according to rumours.
Hell, you can even be allies with come the apocalypse stuff but you have to have a 12" gap in the deployment and if you go within 6" you might fight each other. Again, according to rumours.
Edit - Unbound means you just pick and chose what you want, for example-
5 riptides
1 Imperial Knight
1 Wraithknight
legal force. Lolz had by all.
Hell, you can even be allies with come the apocalypse stuff but you have to have a 12" gap in the deployment and if you go within 6" you might fight each other. Again, according to rumours.
Edit - Unbound means you just pick and chose what you want, for example-
5 riptides
1 Imperial Knight
1 Wraithknight
legal force. Lolz had by all.
40k- Space marines(5000 pts) Imperial guard (3000 pts) Tau (3000 pts)
Epic 40k-Space marines/Imperial Guard(2000 pts)
Infinity Yu jing (Aprox 1000 pts)
Necromunda Escher Mad capsules Avalanche
Blood bowl Skaven
Epic 40k-Space marines/Imperial Guard(2000 pts)
Infinity Yu jing (Aprox 1000 pts)
Necromunda Escher Mad capsules Avalanche
Blood bowl Skaven