Looks like the cash and miles combo for award flights is for more than just Avianca/Taca flights. I checked booking awards with United through LM... just a standard USA award.. offered *limited* flights on UA for 10,000 miles plus $191.00 cash.
Also should be noted that AV/TA requires a minimum flown miles on their metal for elite. Three levels of elite status require 5K, 10K, and 15K respectively on their metal to qualify for their elite.