No difference in who you use as far as I know, I used Crew/HACS. The contracting agency will(should) screen your resume/application before they kick it over to AJX/V. I would say they decide based on your application if they want to see you, but then again I may(probably are) be wrong. I see the mins for an interview posted on all the contractors websites so I will say the 3,000tt is hard as is the requirement for a command type rating.
Good luck