The buyback anomaly survives when using the five factor Fama and French (2015) and the four factor Stambaugh and Yuan (2017) models: buyback announcements are followed by positive long-term excess returns that are positively related to (idiosyncratic) volatility, inconsistent with the low volatility anomaly. The results are consistent with the costly arbitrage hypothesis (Stambaugh et al., 2015) as well as with the market timing hypothesis: the option to take advantage of undervalued stock is more valuable when firm value is more uncertain or is more driven by company-specific information. Combining volatility with undervaluation indicators proposed by Peyer and Vermaelen (2009) improves the predictability of excess returns after buyback announcements.,
Journal of Corporate Finance

Evgeniou, T. (Theodoros), Junqué de Fortuny, E., Nassuphis, N. (Nick), & Vermaelen, T. (Theo). (2018). Volatility and the buyback anomaly. Journal of Corporate Finance, 49, 32–53. doi:10.1016/j.jcorpfin.2017.12.017