First of all, name one company, in history, that's maintained an actual monopoly by fair means, EI, without crossing any boundaries not crossed by their competition.
If this magical company can supply a good product, for competative prices, maintaining a well-paid workforce and not wronging anybody(which, again, is impossible, because actual monopolies always end up screwing somebody) then why break up the company? Just for the sake of giving 'the other guy' a shot? Why? Let the 'other guy' be smarter and win fairly.
This question presents an impossible hypothetical. IN reality, government intervention becomes inevitable because monopolies generally don't get there by playing on an level field.