> You can't because it's a bs metric like "culture fit".

I'd disagree. An indirect metric is "Can I as the technical lead [1] communicate effectively with the candidate?" If the leadership is stable, then a "yes" to this question is likely to imply "yes" to the "getting along" question. If all "subordinates" can effectively communicate with the "hub" (lead), it's not unreasonable to expect that they'd be able to get along with each other using the same mode of communication they use with the lead. That's what my intuition tells me. May be wrong though.

[1] Presumably, the technical lead takes part in the interview process.