In this new broken up set of companies, what's stopping them from remerging like Bell? Also, what's stopping them from giving each other favorable partnerships?
Personally I find this entire exercise a waste of time - rather than break up Google we should just acknowledge that certain industries have certain types of attributes that result in necessarily "anti-competitive" behavior. In Google's case, since it's an internet company I would say the more users it has the harder it is to beat - with that being said they should just create some sort of progressive taxation as a function of users.
Your users in the USA equal 90%+ of the country, you are subject to rules A. Your users in the USA equal to <10%? You are subject to rules B and are subsidized directly by those whose users equal 90%+. If all companies are less than 50% than we use rules c, for example.
The same logic could be used for manufacturing, utilities, internet providers, and more.