This works on War Machine only.
At the Troika aim it to the left and a little up, then get off it and walk backwards until you almost fall off the elevated platform.
Once there walk to the right a little bit (don't fall off platform), now do the chainsaw glitch - press A and B while facing the Troika until you're floating, then walk left while you're still floating and keep pressing X until you grab onto the Troika.
Congratulations your guy is now ducked down, turned around with his arms crossed behind him, while holding onto the Troika. Yay!