The project management plan for implementing drive-thru windows at McDonald's stores involves creating a communication management plan that takes around 3 days to prepare and will be followed until the project is completed. The plan outlines different types of communication, including report updates, announcements, meetings, and presentations. Additionally, a resource management plan is developed within 2-3 days, outlining employee responsibilities and roles for completing tasks efficiently. Overall, the project management plan aims to maximize profitability and sustainable competitive edge by satisfying customer needs.