Can I enable hiding the dock on my MacBook monitor only?
I was able to use the previously suggested ControlPlane app along with some simple shell scripts to get this working.

First, I created a context for having my Thunderbolt Display plugged in ("Desk"), and one that negated that choice ("Lap"). Next, I made two simple shell scripts to toggle the autohide setting and restart the Dock. I put them in a .controlplane directory in my home folder.

~/.controlplane/dock-hiding-on.sh

defaults write com.apple.dock autohide -bool true &amp;&amp; killall Dock

~/.controlplane/dock-hiding-off.sh

defaults write com.apple.dock autohide -bool false &amp;&amp; killall Dock

I then set those files to be executable. 

Lastly, I set the correct script to run for the appropriate ControlPlane context. (Note: I had to show hidden files in the dialog with "⌘+⇧+.")