Hello,
this is a tricky question.
Generally running an older version for rendering something that was created with the newer one is always a risk. I would advise against it.
Given the fact that hotfix 2 and hotfix 1 are very similar, the risk is significantly reduced as opposed to e.g. v7 and v6. However, saying "specific tool that only appeared in Hotfix 2" is problematic, because that version is primarily dedicated to R25 support and minor internal tweaks, so it is still possible that your friend is in fact using a "specific tool", albeit an invisible one.
tl;dr - I'm not sure, this is largely scene-dependant, I recommend first trying to imitate the setup via Team Render. Then it is up to your friend if they want to "take the gamble".
Thanks,
Jan