After re-reading the summoning rules, I'd say no.
The relevant rules:
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At the start of that formation’s action, before the action test dice roll is made, the formation may summon daemonic units from the Daemon Pool.
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Summoned units count as part of the formation for all rules purposes as long as they remain on the battlefield.
The relevant FAQ:
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Q:At which point in activating a formation is the decision to summon daemons made? Can I summon daemons and then declare which action a formation will make?
A:The decision to summon daemons is made between Step II of activating a formation (declare which action it will carry out) and Step III (the formation must then pass an action test to see if it carries out the action successfully). So you must declare the action before you summon daemons.
The declaration of the formation's action happens before the summoning.
Before the summoning happens, there wouldn't be any friendly formations within 5cm to be able to use the Commander ability with.
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