Unions historically were organized by people that were individually very replaceable, could not find easily another job if fired, had limited education and means to fight for their rights and improve their condition.

For this reasons ther employers could force upon them punishing work conditions and contracts, and unions allowed workers to leverage their number electing representatives that could organize them and would be better suited to negotiate with the employers.

I fail to see any connection with engineers which can easily move between jobs, command decent salaries and benefits and are more than able to negotiate better conditons individually with their employers.

Maybe a more suitable organization would resemble the medieval artisan and merchant guilds...