Way to unlock: You need to complete main mission 65 (Architect's Plans) and select the variant that assumes dressing up as firemen (Fire Crew), towards the end of this mission. There is no marker on the map for this mission and you can start it anywhere.
Playable characters: Michael
Additional information: The only premise of this short mission is to steal the fire truck. After you do, you will have to deliver the truck to the marked place.
I recommend against searching for the fire truck in one of the fire stations spread around the game world, because this will render you unable to complete this mission in 100%. Instead, stop somewhere near Lester's clothes factory, produce your phone and dial 911, or select the Emergency Services from the contacts list. After you call them, confirm that you want to summon the Fire Dept.
Wait for the fire brigade to arrive and steal the Fire Truck. Of course, you need to realize that this will alarm law enforcement so, soon after you obtain the truck, hide in some side-alley to wait through the pursuit. After it is over, drive the truck to the clothes factory and park it under the bridge.
Rewards for the completion of the mission: none
Requirements for the completion of the mission in 100%:
- What is your Emergency? - You need to select the Emergency Services number and make the fire brigade to arrive.
- Not a Scratch - You cannot visibly damage the fire truck. Try to avoid the police pursuit and wait in a secluded spot until the law enforcement loses its interest.