Coming in a bit late to this discussion, but I don't see how "social distancing" is compatible with public transport. The capacity of planes, buses and train would be reduced to an extent to make the service economically unviable, and bordering on completely pointless from an environmental and traffic reduction POV.
I think the answer is that we have to learn how to live with the virus. That means lockdown until there are very few cases, and a huge investment in contact tracing and enforced quarantine until tested & proven virus free for people who have been in contact with an infected person.
The mooted apps and phone tracking would be an ideal way of doing this. In time you'd be able to use the data to hone the response "so, we know that actually the chance of infection is almost zero unless you are within x metres of y minutes", and you could flex the alert threshold up and down dependant upon levels of infection - so as infection gets to very low levels you widen the net to really find that last few infections and work toward eradication.
Problem is the civil liberties lot won't allow it. I'd far rather we had mandatory location tracing and enforced testing and quarantine than stupid passive measures such as mask wearing.
The media are obsessed with "When will lockdown be eased". That doesn't interest me - the truth is nobody knows yet. What's far more interesting, and not being asked, is "What next? How do we prevent the virus spreading again once we have achieved low levels of infection, accepting that continued significant social distancing, business closures and curbs on leisure activities are undesirable and unfeasible in the medium to long term?"