I just ran into this issue today during a migration. Simply put how do I get an answer file into a new VM? The process is simple.
1. Using another VM, add a floppy drive and select the option to create a new floppy image.
2. Boot the VM and once loaded open the floppy and format it.
3. Copy your SBS answer file to the newly created floppy.
4. Using the VMWare console remove the floppy from your running VM.
5. Once your new SBS 2011 VM gets to the point where you can choose either a new install or migration, select Migration.
6. At this point on the console click to add a floppy and then select your new floppy image from the datastore that contains the answer file.
7. From there continue your migration.
This is a quick easy step to allow your to get the migration answer file loaded without the need for any 3rd party applications or other issues. It keeps the disc stored on the datastore with your other ISO files and is there for future use if needed.
Good luck with your migration.
**Update: Make sure you removed the virtual floppy image before your next VM restart**