Is it possible to download sandbox projects with Drush?
It's possible to download sandbox project with drush using make file.

Here is example.make file:

core = 7.x
api = 2
; Sandbox module
projects[range_field][type] = module
projects[range_field][download][type] = git
projects[range_field][download][branch] = "7.x-1.x"
projects[range_field][download][url] = http://git.drupal.org/sandbox/Taran2L/1848632.git
projects[range_field][download][revision] = a1cc04da3c1dd957e6808b7e6a381c5970904863


Then you can execute it via:

drush make --no-core example.make # optional options are: -y --working-copy --no-gitinfofile --verbose