No, that routine does not support the keyword for converting interleave. The tasks have been modularized in many ways so you would need to export a new raster with the interleave you desire. For example:
raster=e.OpenRaster(file)
newfile=e.gettemporaryfilename('dat')
raster.export,newfile,'envi',interleave='bip'
However, there is no FLAASH API. This is a UI tool only. You could use Quac instead.
http://www.harrisgeospatial.com/docs/...