Doesn't look like you can - type the following at a command prompt to see the full list of options:

     tabcmd help commands

you can also do the same with tabadmin:

     tabadmin help commands

Technically no but that shouldn't stop you from achieving what is needed.  If you define your permissions at the project level and create a project for every combination of permissions then which project you publish to will determine that workbook's permission. 

I can't understand, why there is no option available to set permission using TabCmd?

Tableau is really very un-reliable. Hope so it will be added in next version.

I highly doubt this will be an option in tabcmd in the future for two reasons.

1.  There are too many configuration options to be feasible in a command line interface.

2.  It already does allow the user to set permissions by inheriting the project's permission that you are publishing in.

Like stated above, when using tabcmd, you can specify the permissions of a workbook by creating a project with that set of permissions and publishing in to that project.  This is why it is very important how you set up your security model initially.

Not sure how this issue could be described as "un-reliable.".....does using tabcmd causing your server to crash?

Yes. I have a C# API(uses TabCmd) service to manage the operations like add/update/delete users from my application. Using Tabcmd makes my server very slow and I have to restart server most of the time to kill the background tasks to avoid the bottleneck. Please check the screen shot attached. It has many background tasks in Pending status.