Beware the Attack Basset
Methinks you've made underestimated the cult-like brand loyalty. Then again, what people say they actually do isn't particularly equal. If it were, millions of DIRECTV would have cancelled the instant that the AT&T takeover was consummated.It really isn't a battle to the death.
Having one company manage the whole wad would axe a lot of the most expensive employees. That's a synergy. Being able to consolidate billing, support and installation functions are all synergies that may not lead to halving the workforce but they will likely significantly reduce the costs. Over time the synergies and advertising efforts could be more finely tuned to address a smaller set of competitors.