Hi,
Thanks for the interest in our plugins. I can answer your questions.
If you can create an iCal File you could use the iCal Importer to import events into the Events Calendar. It could also be done with a csv file.
As for this:
Another functionality they have asked for is to have a button on each event, that the staff could select it and say that they are available to work on this day?
It might be possible with a customization, but it is not a feature we have and can support.
Let me know if you have any follow up questions.
Thanks