Apocalypse (8th) - Transport and Detachments

[Valkyrion]

Am I correct in assuming that the rules for transports don't prevent units from one detachment starting the game embarked on transports that belong to a different detachment?

 

For example, a Supreme Command detachment cannot include a Heavy Support slot, so if I want my 3 hq's to ride a Land Raider I have to second that land raider from another detachment. 

Once the game has started I understand that nothing precludes me from embarking said Land Raider, but because you deploy one detachment at a time I don't know how the rule interacts. 

Would I deploy the detachment which has the Land Raiders in it first, and the then deploy my Supreme Command within that detachment? Is that allowed?

[Tyriks]

I missed that this is an Apocalypse question, please ignore this. Edited March 26, 2021 by Nemesor Tyriks