Can an alias be added to the dock via the command line?
Definitely scriptable with terminal commands.

/usr/libexec/PlistBuddy -c "Print" ~/Library/Preferences/com.apple.dock.plist


Shows you the actual configuration for the dock.

Within the above file you need to modify the "persistent-others" array if you want to create a "file" alias.

This is done the following way:

/usr/libexec/PlistBuddy -c "add:persistent-others:0 dict" ~/Library/Preferences/com.apple.dock.plist


If you want an application alias you will need to modify the "persistent-apps" array.

Once you make the changes and you are testing you need to do:

killall dock


to refresh the dock.