Both players would receive 3 BRs.
Each attacking team is resolved separately. If the attacker swung with 3 teams and each team won an Outstanding Battle Reward, you still resolve each battle separately.
Here's how it breaks down: Team 1 is winning 2 BRs. m792 would convert that to 2 damage which is dealt to n1382. n1382 would convert that damage to 1 BR. So Team 1 would win 1 BR. Repeat for Teams 2 and 3 for a total of 3 BRs.