1. BIS polling interval for Hotmail accounts is typically 15 minutes. Perhaps your Windows-based phone polls more frequently than that?
2. Do you have Wireless Reconciliation enabled for your Hotmail account? See here for detailed instructions: View Document
According to this KB article, it should be possible to do what you're looking to do: KB05133 - Email reconciliation features for the BlackBerry Internet Service - Port3101.org : Your BES Connection