They didn't really explain how technically amazing the play was. Basically team B came in with the mass sleep spell to get everyone in position for the team fight. There's basically a second in between that and the "ravage" spell that tidehunter casts to damage and stun the whole team (it's the ability you see where all the tentacles come out of the ground and knocks everyone up in the air). In that really small amount of time in between the sleep ending and the ravage spell being cast (a vacuum was cast in better en them to pull all of team A together for the ravage), a member of team A was able to activate the active ability on their black king bar item (gives you magic immunity), making them immune to the ravage spell. This enabled him (enigma) to cast his black hole ultimate right after, which damages and disables all of them while pulling them towards the center. Another hero, rubick, was able to use force staff (which pushes you a certain distance in the direction you're facing) to get out of the ravage range. Also, he has an ultimate which basically steals the last spell an enemy hero casted. He used it on Tidehunter after ravage was cast and recast it back on the other team after they had been black holed. A third hero, juggernaut, used his whirlwind ability after sleep ended to make him magic immune as well, allowing him to attack the enemy team as well. It really was just amazing teamwork and recovery.