I eventually managed to solve the problem by building a default formula using a XPath expression that fetches the teamID in the Persons list :
xdXDocument:GetDOM("Persons")/dfs:myFields/dfs:dataFields/d:SharePointListItem_RW/d:Team[../d:Person/pc:Person/pc:AccountId = xdXDocument:get-DOM()/dfs:myFields/dfs:dataFields/my:SharePointListItem_RW/my:Person/pc:Person/pc:AccountId]
xdXDocument:GetDOM("Persons")/dfs:myFields/dfs:dataFields/d:SharePointListItem_RW/d:Team[../d:Person/pc:Person/pc:AccountId = xdXDocument:get-DOM()/dfs:myFields/dfs:dataFields/my:SharePointListItem_RW/my:Person/pc:Person/pc:AccountId]