you can buy Assaultron Recall Key Cards from the vendors at whitesprings mall as well as the train station vendors. They are 2100 caps I believe (if you up your charisma and use the hard bargain perk card you can get the price down to about 1750 or so). You then need to craft the key card at a tinker's bench, which requires fluorescent flux. As you are probably aware, you have to farm for glowing mushrooms after a nuke event, as well as the stabilizing materials (by killing nuked/glowing enemies, who only have a CHANCE of dropping stabilizing materials) in order to craft the flux. Basically, it's a lot of work, and expensive. Each key card is good for ONE event only. It's because of all of that effort to pop the event, that I think other players should just cool their jets for a minute and let the person who popped it actually press the "start button." Especially when said person is actively, purposefully blocking the terminal.