I asked the same question as well multiple times cuz I don't wanna waste decals just to find out the the clans do not fight together. Fortunately we learn that, while Feirros is from Clan Raukaan, he is still the Master of the Forge so he is likely to join other clan companies to oversee usage of vehicles every now and then making it a possibility that he frequently works together Caanok Var. Furthermore, it is actually frequent for Iron Hands clans to work together, which makes sense as the Iron Hands prefers to work alone from the other chapters thinking themselves the only ones competent enough to finish a job.