No, only the unit that rolled low and received the combat scenario is the one that looses movement, the reinforcing units continue on and get their full movement potential, plus can take part in the battle. The turn reinforcing units arrive is relative to how many map tiles they have to travel to get to the combat area. If they die as reinforcing units I do not retcon (remove) any territory they would have captured on their movement orders.
So let me outline an entire example scenario for combat generation:
"Your" Crab CRB-27 starts at AA111 and moves AA112,
AA113, AA114 and ends at AA115. The Crab moved four total map tiles, all are neutral territory no player owns. That means there are FOUR rolls for potential bandit spawns. The roll for moving through map tile AA113 turns out to be a 2 of 100, so a combat scenario occurs.
Noting this is a medium mech it will most likely be a "combat" scenario, but I have others in my bag of tricks. Let's say this happens to be a special one, a "Bounty Hunter" mission. The objective is to destroy one particular bandit enemy, and you also get a cash bonus for it. (Mini boss?) Anything killed, as long as you claim victory, could be potential salvage.
I look at the terrain and biome data of the map tile the combat is in, and the surrounding tiles as well, this determines the details of the map you fight on. The weather conditions/day-night, are random rolled based on the climate for the biome. (Hint: Tornado's will be extremely rare). If the battle is just very slow units, like infantry, the map size may be reduced.
Then I look for reinforcing units of player control.
You have a Bashkir C starting at AB108, moving AB109, AB110, AB111, AB112, AB113, ending at AB114. Since it moved through an adjacent map tile, AB113, it can participate as a reinforcement. It has to move through AB109 to AB112 before reaching AB113, thus it needs 5 movement to reach AB113, and can arrive on TURN 5 of the battle. If it takes part in the fight or not, as long as it survives, it will end its turn at AB114.
You also have a mixed lance consisting of a 2x Bulldog (AC/10) customs, 1x Panther PNT-9R, and 1x Javelin JVN-10N, they start in AC113, move through AB113, AA113, to end in Z113.
These too are reinforcements, and even through they have different speeds as individual units, are traveling together. They can arrive on turn 1, since AB113 is a reinforcing hex. After the fight win or loose they would end the turn in Z113. (Unless you are fighting humans, and loose you get the rest of your movement, there are some select cases against humans that you do not.)
Furthermore there was a Goblin Infantry Transport with a loaded Foot Platoon (Rifle) that started its movement directly in AA113 this turn, traveling to AA117. It too can "reinforce" and arrive on Turn 0 (Starting turn), and will end its movement at AA117.
Next I determine enemy forces, given there are far more reinforcements than the starting unit, the battle value of the entire player force (the Crab, Bashkir C, mixed lance and Goblin>Infantry) is used to generate an equal battle value or sometimes more of enemies.
Also note a reinforcing unit cannot reinforce twice. If two different combats happen along their planned travel route, they can only reinforce the first scenario.
