Bevflex 224 is not a Barrier tubing. Highly likely that the tubing has picked up the flavor from the margarita permanently. Unfortunately whoever encouraged the retailer to put the margarita on the beer system did not warn them on this issue.
It is always worth a try though to clean the line with a 3% caustic (circulate) and cross your fingers and hope for the best.
Scott Zuhse, Instructor
Micro Matic Dispense Institute