Bengal's inept batting coupled with the defensive strategy to shave off the green top on the eve of the match brought the home team's downfall as it was bundled out for a paltry 185 in 47.4 overs.
In reply, Railways openers feasted on the Bengal attack to put on a 109-run partnership with Amit Paunikar scoring 83 (86 balls; 14x4) before Ashok Dinda gave made the first breakthrough in the 22nd over.
Railways had last won the title in 2005-06, while their Sunday's summit clash opponents Karnataka are yet to win the one-day crown.
The big win also avenged Railways' Ranji quarterfinal loss to Bengal and it was the home side's successive semifinal exit. Bengal had lost to eventual runners-up Maharashtra in the Ranji semifinals.
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The strategy backfired after Bengal put up a listless show after opting to bat. Railways pacer Anureet Singh (8-1-22-1) once again set the tempo while spinners Chanderpal Saini (3/25), Karn Sharma (2/41) and Ashish Yadav (2/25) backed up well.
Manoj Tiwary (61 from 95 balls; 1x4) showed positive temperament but he did not get enough support from his teammates, forcing him to play a restrained innings. He scored his first and only boundary off the 81st delivery.
Brief Scores:
Bengal 185; 47.4 overs (Manoj Tiwary 61, Shreevats Goswami 38; Chanderpal Saini 3/25, Karn Sharma 2/41, Ashish Yadav 2/25) lost to Railways 188/5 in 38.2 overs (Amit Paunikar 83) by five wickets.