You'd think the unions around here would be against the illegals undercutting them buy working for less wages, but the union leaders around here see them as new, dues paying members. The unions have sold out completely to the Dems and their moonbat agenda.
And in any case, the city unions here are good at, um, ensuring that "scab" job sites are picketed and effectively shut down.
Recruiting illegals for a union is just a dumb move probably done in desperation. The fact of the matter is, a good union could dry up/reduce jobs for illegals.
This will probably never happen, except in places where it has already happened.