It's a sort of two-edgded sword if it's not managed correctly.

Think if Google got bigger and wasn't as nice - A monopoly in virtually all technology sectors, charging prices whatever it feels like with little options or competition, particularly if it held "business deals", aka a cartel in the industry with Apple and Samsung and Windows.

But restricting growth of companies can create a more localised problem, like the US' internet troubles. Limiting expansion or growth means an area might only have one option, meaning that company can impose whatever the fuck it likes unless you're lucky to have more than two companies in your area.

I'd say something along the lines of how telephone companies work here in the UK is fair - Allowing companies to share the wires of another (e.g. TalkTalk and others using British Telecom wiring), means you can still allow companies to expand as far as they like, but that area is overlain with other companies also, regardless of size. This in fact would aid start-up companies as it saves them money building up infrastructure when they can share the rest, and improve on areas they control. The only places with limited choice would be isolated areas such as mountainous Wales and Scotland, where there is choice but just not much improvement in quality over the other due to limited infrastructure and investment in the area.

On the downside, this could hamper overall development, as BT doesn't want to improve the wires at their expense when everybody else is going to freeload off it.