Jacobs, J. L. et al. (2009)
Only 32 people and only long enough for two colds. There was almost no chance of achieving statistical significance there.
There were found to be more headaches in the group wearing masks. That's wearing masks for eight hours a day. The public scenario is concerned with shops, transport, crowds not so much eight hours a day. Conceivably the effectiveness is also a function of duration of exposure.
Cowling, B. et al. (2010)
The ACL has been pretty selective in fishing out a little quote from inside this (paywalled?) study. At the same time they omitted this, from the abstract:
"There is some evidence to support the wearing of masks or respirators during illness to protect others, and public health emphasis on mask wearing during illness may help to reduce influenza virus transmission. There are fewer data to support the use of masks or respirators to prevent becoming infected."
Ie, there is likely a benefit in protecting others. They didn't seem to want to say that.
bin-Reza et al. (2012)
“There were 17 eligible studies. ... None of the studies established a conclusive relationship between mask ⁄ respirator use and protection against influenza infection.”
Contrived wording is often a giveaway - this is spin. A systematic review is supposed to weigh up the evidence together. No study can establish a conclusive relationship.
The ACL omit this finding from the abstract:
"Eight of nine retrospective observational studies found that mask and ⁄ or respirator use was independently associated with a reduced risk of severe acute respiratory syndrome (SARS)."
Smith, J.D. et al. (2016)
".... we found no significant difference between N95 respirators and surgical masks in associated risk of..."
They were comparing masks - not evaluating whether to wear a mask. But on that subject they say:
"Transmission of acute respiratory infections occurs primarily by contact and droplet routes, and accordingly, the use of a surgical mask, eye protection, gown and gloves should be considered appropriate personal protective equipment when providing routine care for a patient with a transmissible acute respiratory infection.1–3"
That's as far as I got...
It's also worth considering whether the source (ACL) may have a conflict of interest. A civil liberties group rushing to oppose masks during a pandemic may not be objective - and it seems here that they aren't.
My own view is that masks surely reduce the amount (load) of virus transmitted to others, especially if the proximity doesn't last very long. Until it's disproved by evidence that'll do as a default for me.