I don't think given the operating structure there are going to be TW layoffs resulting from duplication and redundancy.
Layoffs at the legacy AT&T businesses (Donovan) will continue and likely accelerate to pay for the merger. Where the TW people are going to feel it is from implementation of AT&T's bureaucratic policies.
The belief is that TW is under performing and needs "encouragement". That's the reason AT&T is willing to spend the equivalent of 1/3 of its market value to acquire. Right now, TW would make up less than 20% of AT&T's total revenue. So they are either grossly overpaying or believe TW's assets are under valued relative to the earnings and cash flow. Or both.