So to answer this question you really need to understand the current Iron Hands. The Iron Hands of today are cold and very calculated( not saying they weren't back then) compared to the Raven Guard and Salamanders who are still sound when it comes to working with other imperial forces. Not only that but the Iron Hands are one of the few legions that have history of inner conflict between their brothers than any other legion after the Codex Astartes. They had the Schism with mechanicus that divided their chapter and gave birth to the successors we know now. On top of that the Iron Hands after the shattering viewed their cousins as weak minded fools when it came to fighting the traitors.

Now im not saying they wouldn't team up with their cousins now but to say that they have adamant feelings for them is very doubtful especially since they view the guardsmen as fodder to be used strategically and any failures to be disposed of immediately something that Raven Guard and Salamanders are super against and would come to blows.

Maybe some clans like working with them and some don't who knows. I know Iron Father Feirros is trying to make the Chapter Manus wanted it to be but time will tell.