The quote below is from "Professional and Home-Made Face Masks Reduce Exposure to Respiratory Infections among the General Population". There's enough studies looking at this for SARS and influenza- including for the general population - that it is highly irresponsible to err on the side of not using masks even if there's no clear evidence for population usage for SARS-2.
"Opportunistic data collected during the SARS epidemic in Asia suggested that population-wide use of face masks may significantly decrease transmission of not only SARS but also influenza [3,4,5,6,7]. As part of pandemic preparedness, many are contemplating the contribution wide-spread use of masks could have [8,9]."
3. Lau JTF, Tsui H, Lau M, Yang X (2004) SARS transmission, risk factors and prevention in Hong Kong. Emerging Infectious Diseases 10: 587–92.
4. Lo JYC, Tsang THF, Leung Y, Yeung EYH, Wu T, et al. (2005) Respiratory infections during SARS outbreak, Hong Kong, 2003. Emerging Infectious Diseases 15: 1738–41.
5. Wilder-Smith A, Low JGH (2005) Risk of respiratory infections in health care workers: lesson on infection control emerge from the SARS outbreak. Southeast Asian Journal of Tropical Medicine and Public Health 36: 481–488.
6. Wu J, Xu F, Zhou W, Feikin DR, Lin C-Y, et al. (2004) Risk factors for SARS among persons without known contact with SARS patients, Beijing, China. Emerging Infectious Diseases 10: 210–16.
7. Tang CS, Wong CY (2004) Factors influencing the wearing of facemasks to prevent the severe acute respiratory syndrome among adult Chinese in Hong Kong. Preventive Medicine 39: 1187–93.
8. World Health Organisation Writing Group (2006) Nonpharmaceutical Inter- ventions for Pandemic Influenza, International Measures. Emerging Infectious Diseases 12: 81–87.
9. World Health Organisation Writing Group (2006) Non-pharmaceutical Interventions for Pandemic Influenza, National and Community Measures. Emerging Infectious Diseases 12: 88–94.