I guess it could be an argument about what corruption means, but I think that people underestimate how dysfunctional the legislative and regulatory processes can be even without any legal violations.
To put it another way: look at the regulations Google demands exemption from in return for building fiber: build-out requirements, slow permitting, etc. Did the incumbents lobby for these things? No. They arose out of municipal politics that have little to do with lobbying.
Even Wikipedia says:
Regulatory capture is a form of political corruption that occurs when a regulatory agency, created to act in the public interest, instead advances the commercial or special concerns of interest groups that dominate the industry or sector it is charged with regulating.
I don't think I could say it better. Regulatory capture is different to lobbying because the regulatory agencies act in the interest of the company instead of the public. Lobbying is when the company puts forward its own interest.
In every city I've studied, incumbents are bound by the same requirement to build-out their network as potential competitors. I'm sure there are exceptions to this, but the only one that comes to mind is Google Fiber: they get a pass on build-out requirements. These requirements curtail the most obvious route to competition: deploying in dense, rich neighborhoods where the incumbents generate most of their profits.