The press has reported on an imminent merger of O2 and Virgin Media (UK). This is not likely to be driven by the pursuit of revenue synergies as dis-synergies are more likely if the brands are merged.
Cost synergies are real, albeit a bit tangential. However, in a mature market even modest synergies are worth pursuing.
A full regulatory review may be required but approval is likely. Market impact is somewhat nuanced, with the benefit of a distracted competitor short-term and a larger but still rational operator ultimately.