Motion Pro 02-0008 is the "Push" cable I use on my 500 and 550.
It's good to have this cable for a few reasons. Like you said, a stuck throttle. But also (this happened to a friend of mine), if you're "Pull" cable ever broke, you can snap the push cable in it's place down at the carbs and reverse throttle it back to your destination, somewhere it can be fixed, or simply back to safety.