Yes. You would report the cash in lieu on your tax return. Keep in mind, although the amounts may be small, they do have a cost basis since they are fractional shares, i.e. you would not pay tax on the whole amount.
If your shares are being held by Computershare you should be able to find a 1099-B or gain/loss info there.
Your AT&T share basis for the remaining shares would be split between your existing T shares and new WBD shares.
AT&T has an online calculator to calculate the allocation of your cost basis between AT&T Inc. and WBD common stock.
See Cost Basis Guide
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