Don;t think its possible. We had looked into this ourselves at one point and couldn't locate anything in the API for that. I have heard that in version 9 JAMF will add a number of additional items you can pull from the API, but Removable MAC addresses is currently not there. I'm not sure if it will be one of the new items added or not.

it isn't possible with rest.
it's trivial with sql!
i created a new mysql user that only has read access to the removable MAC table, then wrote a one line sql script that dumps the table to a text file in a share, and set up a scheduled task on the server to run that sql script every 5 minutes.
the whole setup took about 10 minutes to create and test.

Thanks mm2270, and thanks for the SQL tip nkalister. If the info isn't available in v9 we may do that.