While possible I doupt they will. You sabotage your competitors in congress if you can. However operations like this should be allowed and even cheered.

The worst case now for Boeing is a series of disasters that leaves the public unwilling to fund anymore space thus killing not only SpaceX, but also Boeing. If Boeing sabotages SpaceX not only do they risk that they also risk getting caught by the investigation which would be bad for Boeing. Note that unsuccessful sabotage meaning you are caught is a real risk as well.