In the list of features, it says specifically that Exchange Server 2007 is supported through EWS:
Microsoft Exchange Connectivity
The Bat! connects to Microsoft Exchange Servers using EWS protocol or native MAPI protocol to fetch or send messages. There are two ways of connecting to Exchange Servers via MAPI: using MS Outlook's profile or Microsoft Exchange Server MAPI Client and Collaboration Data Objects. EWS allows accessing MS Exchange Server 2007 and later versions directly with no need for extra applications. The Bat! downloads not only emails, but other Exchange items as well, such as calendar events, contacts, tasks and notes in EWS accounts.