A new framework for unionizations means that a company must voluntarily recognize a union or demand an election—and can no longer interfere with the election.
Union busting is already illegal, and corporations have been getting away with it the entire time because there is essentially zero enforcement 99% of the time, and even in the rare cases where there is enforcement the penalties are 1/1000th the cost of unionisation. There's no reason this will change.
I imagine proving union "busting" intent is also very difficult, as they use various tactics that could be considered standard practice in the eyes of the law (e.g. closing stores).