I don't think re-enforcements will be costed during a fight mate, I am reading the article now and it looks like it will work this way:
You start out in a chapter battle barge above the planet
You click on a risk style map of areas
Each area reveals what the mission is, what is required of you and what is at stake.
You then kit out a full force based on a certain amount of points ala table top
And then you enter battle via drop pods
You can land all pods at once or you can add them as you need them re-enforcing certain areas and situations as they come up.
eg you may land a single squad of marines to check an area, get swamped by orks and land a drop pod containing a Dreadnought right in the middle of them causing hit damage and unleashing the Dread
