Can Drush be assigned as a ssh users default shell? Problem:
I need to allow ssh access to my web server to dev team in order to use Drush. I am reluctant to give them full SSH access due to lack of trust in their SSH skills and knowledge. 

Attempted Solution:
I tried creating users on my server and only allow them access to Drush using the following command. 

useradd -s /usr/bin/drush drushuser

On logging in with drushuser, a list of commands displays and logs out immediately.

I do something similar with git and git-shell, I set the /usr/bin/git-shell as their default shell and it does allow them to push and pull content remotely. 

Is there any way I can get the same results for drush?
Drush has some sort of interactive shell - try drush php:cli. (You would created a script /usr/local/bin/drush-shell similar to git-shell.) However, I just tested and it doesn't seem to work for Drush 9. If you are still using Drush 8, it seems to work just fine (as drush core-cli). Disclaimer: I haven't actually tested this as a login shell.

The other more standard approach is to use lshell and set it up so Drush and needed tools can be used. I haven't tested this either - sorry.