Is there any way to run Network Link Condition from a Standard User account?
You can start the System Preferences.app as Admin and from that use the Network Link Conditioner.prefpane.
To do so use the following shell command:
sudo /Applications/System\ Preferences.app/Contents/MacOS/System\ Preferences

or the following AppleScript command:
do shell script &quot;/Applications/System\ Preferences.app/Contents/MacOS/System\ Preferences&quot; with administrator privileges 

When I click on the Network Link Conditioner in the window that is opened after the password is given, I get a message that System Preferences needs to be restartet to open the PrefPane. After agreeing to this the Network Link Conditioner is working for me while I'm logged in as normal (non-admin) user in 10.10.
In macOS Big Sur, the command is
sudo /System/Applications/System\ Preferences.app/Contents/MacOS/System\ Preferences