Churchill now have three wins from four games while the Kolkata-based side dropped to third with eight points from five.
The game looked like meandering towards a draw but Plaza struck his fourth of the season after coming close on at least three occasions earlier in the game.
Churchill’s Portuguese coach Fernando Tavares rang in wholesale changes as did his Spanish counterpart Alejandro Menendez Garcia.
East Bengal were playing after a long three-week break but Churchill’s previous outing was a heartbreaking last-minute loss to the Indian Arrows.
The visitors earned five corners compared to Churchill’s one in the first half-hour. The referee also had a busy half having to flash his card as many as three times. It ended with a Plaza flash strike but the scoreline remained goalless.
Plaza tried to break the deadlock in the 62nd minute but missed from close, two minutes later, he hit the crossbar.
It was Bengal’s turn to hit back with Crespi’s crisp right-footer thudding the Churchill bar in the 85th minute and Espada, a minute later, missed the target from a lay-off from Colado.
Finally, a measured cross from super-sub Israil Gurung, who came in late in the second half, found a lurking Plaza who banged it home past a diving Lalthuammawia Ralte to dent the Red & Gold’s unbeaten run.