First of all what are you worried about? As a contractor a union will not even consider representing you. Unions are basically only being considered for the in house techs of the HSP's. Where do you fit into that picture? You don't.
Currently many of the HSP's are moving to fleet vehicles and trying to run off all the POV techs who while eventhough considered in house "employees" are being paid piece rates (like oldschool and I were at Bruister). The HSP's are doing this so they can hire more $10 per hour undertrained FNG hacks. Having a union in these HSP's might keep this from happening or going too far.
Consider this, where are all those seasoned techs that are being pushed out going to go? They are going to move into the ranks of the contractors (if they decide to stay in the satellite biz). And just were is that going to put you? I'm sure you don't want anymore competition for work than you already have do you? What will you do if those former in house techs go to the Prime and offer to undercut your rates? You be wishing then that they had gotten their union and stayed the h*ll where they were, won't you? Face it the more competition you have the less bargaining power you have with the Prime. It doesn't matter who the boss is (Prime or HSP) they don't value your work as much as they value their wallets, if they think they can get the job done cheaper by someone with less experience than you they will dump you in a heartbeat.