Jednostki z rezerw wystawia się tak samo jak byś nimi poruszał, czyli nie wszystkie na raz, tylko pojedynczo, więc decydować się musisz po każdym rozstawieniu. Co do rezerw nie jestem przekonanych, gdyż np. Blood Angele mają stratagem, który pozwala na to samo, a definicja reinfortments trochę się kłóci, bo w takim razie używając takich możliwości w turach 4+ automatycznie po opuszczeniu battlefileda powinny być traktowane jako "slain", a tak nie jest...

Odpowiedź na ostatie kłopoty przyszła w nowym FAQu:

Spoiler:

Q: If the unit arriving as reinforcements is a Character, can the firing unit shoot at it even if it is not the closest enemy unit?
A: No – unless the firing unit is using a weapon that allows them to target a Character even if it is not the closest enemy unit. This takes place ‘as if it were the Shooting phase’, so all the normal restrictions of the Shooting phase still apply.

Q: If the unit arriving as reinforcements has another unit embarked inside it which must disembark after it has been set up (such as units embarked within a Drop Pod, or a Tyrannocyte), can the firing unit shoot at the unit as it disembarks?
A: No – though the unit can shoot at the Drop Pod/Tyrannocyte before the units inside disembark.

Jeszcze odnośnie transportu i DSa:

Spoiler:

Q: The Tactical Reserves matched play rule states that at least
half the total number of units in my army must be set up on the
battlefield during Deployment. If I have units embarked in a
transport, do they count against the number of units I have to
set up during Deployment? If, for example, I have a Valkyrie
with three units embarked inside it that will arrive on the
battlefield during the game, how many other units do I need to
set up during Deployment to satisfy the Tactical Reserves rule?
A: Yes, embarked units count as units in your army,
so must be counted when referring to this rule. If you
have three units embarked inside a transport that will
arrive during the game, you need to set up at least four
other units on the battlefield during Deployment –
equivalently, if you set up three units in a transport on
the battlefield, you could set up four other units to arrive
during the game.