Hi there!
I just released v0.9.4 which has the filters that are needed for your rollover tooltips in the calendar.
To be more specific, you need to use the wpt_calendar_html_day_link filter.
The docs:
@param string $day_link The HTML for the link for the day.
@param string $day The day of the month being displayed in <code>yyyy-mm-dd</code> format.
@param string $day_url The URL to the production page or the listing page.
@param string $day_label The text being shown inside the link for the day.
@param array $events An array of WTP_Event objects. The events that take place on the day of the month being displayed.You can use the $events to add an extra div to $day_link. You can then write some CSS and/or javascript to turn it into a tooltip.
To make it even easier for you to get started I created an example plugin that you can use to write your own plugin. Get it here:
https://github.com/slimndap/wp-theatre-example-extension
Let me know if this works for you. I would love to get some feedback.