The MBTA is actively in shambles, and at various times train routes are being replaced with bus shuttles.

You basically need to brew a pot of coffee/tea, and digest:

https://www.mbta.com/alerts/subway

Before making real plans.

Unfortunately, this is the state of the Bay State. I also don't have my arms around how exhaustive this URL is from a timeline perspective - nothing for April is seemingly cited, but does that honestly mean April won't have any of these planned service outages, or just that they haven't been scheduled yet?