In the second game, Alaska also moved closer of earning a semis berth after escaping with a 104-101 win.
The Aces won despite being outrebounded by the guard-heavy Gin Kings, 58-44.
Mark Cardona actually had a chance to tow the Bolts to victory in regulation, but he missed a hook shot with 4.2 ticks left.
Gabby Espinas then foiled a potential game-winning basket by Peter June Simon to send the game into overtime.
The Llamados were on the brink of defeat twice, but somehow found a way to escape with the win.
B-Meg was down 89-91 in the final minute of the first overtime when Jonas Villanueva sank a floater to tie the count with 21.8 seconds left.
Mark Cardona then missed a triple at the buzzer, allowing the game to go into another five-minute extension .
Derby Ace scored the first four points in the second overtime then relied on Simon and Yap’s shooting to finally put the game away to enjoy a 1-0 edge in the short quarterfinal series.
With the Llamados up 95-92 in the second extension, Simon’s jumper and Roger Yap's three-pointer pushed their lead to eight, 100-92, a minute and 15 seconds left.
Simon erupted for a game-high 35 points while James Yap also had a splendid night, adding 27 markers before fouling out early in the first overtime.
“We expected this kind of game. We know Meralco is a tough opponent, but we managed to find a way and escape with this one," said Llamados coach Jorge Gallent.
“The guys stepped up in the second overtime, especially PJ (Simon). Credit to the guys. They played tough. It was no easy win for us, obviously."
Cardona, who also fouled out in the waning seconds of the game, had a team-high 30 points to go with his nine rebounds and five assists. The former La Salle guard had 11 turnovers, however.
Espinas added 20 points for the Bolts.
Game 2 is on Wednesday, with B-Meg hoping to end the series to advance to the best-of-five semi-finals. – JVP, KY, GMANews.TV
B Meg Derby Ace - Simon 35, J. Yap 27, Villanueva 18, Allado 11, R. Yap 9, Salvador 4, Canaleta 2, Gaco 0, Timberlake 0, Pingris 0.
Meralco - Cardona 30, Espinas 20, Isip 16, Thiele 9, Omolon 6, Weinstein 5, Ross 5, Taulava 4, Juntilla 2, Gamalinda 0, Menor 0, Belga 0, Pacana 0.
Quarter scores: 27-18, 50-36, 69-65, 87-87 (1st OT), 91-91 (2nd OT), 106-97 (Final).