I already had the Windows version of BIAB 2013 when I switched to a Mac earlier this year.

I have some other legacy programs and files from Windows and from Ubuntu whose data I can't port over to the Mac and use with Mac equivalents, so I bought Parallels and run Windows XP and Ubuntu 12.04 when required, as Virtual Machines.

I believe there are a number of features of BIAB for Windows which aren't available in the Mac version, so this solution suits me fine.

I use shared folders on the Mac to store the BIAB files, along with the PDF leadsheets and MP3 backing tracks I've generated using BIAB, so it's simple to synchronise my iPad via iTunes on the Mac side.