Took me some time but I was able to track down how to get aging information out of AX through it’s Business Connector. I’m putting this here as a reminder of how to get it done.

using (var cust = ax.CreateAxaptaRecord("CustTable"))
    //Find the customer you want to get aging info for    
    ax.ExecuteStmt(String.Format(@"SELECT * FROM %1 WHERE %1.AccountNum == '{0}'", acctNum), cust);    
    while (cust.Found)    
        var custVendStats = ax.CallStaticClassMethod(
        cust, //Customer record        
        "", //Aging bucket name goes here         
        2) //Document type        
        as AxaptaObject;        
        var accountSum = custVendStats.Call("TmpAccountsum") as AxaptaRecord;         
        while (accountSum.Next()) //the secret to getting results is to call .Next() before reading.        
            //Do something super interesting with the aging.