Detect from ISPExternalBinaryProvider that read file request is from backup/export proccess

Question

In my sharepoint 2010 instance we use EBS. I would like to modify implementation (from http://technet.microsoft.com/en-us/magazine/2009.06.insidesharepoint.aspx):

1. detect if file read request is from backup or export site (Get Calling Method using Reflection [C#] ? )
2. if true return some small (1kB) mocked file
3. if false return original file

Is it possible?