There've been electronic boards up for the last couple of weeks - I go past one near St Pauls. It's definitely real; it's been on the cards for some time. At the moment it's only an experiment, but I suspect it'll go permanent.
The City corporation, although it's extraordinarily undemocratic and a throwback to the middle ages is in some respect quite enlightened. It has noticed that most people go through Bank junction on foot; from memory cycling is the third most common mode of transport after walking and bus passengering.
It's worth taking a look at some of the background documents:
https://www.cityoflondon.gov.uk/ser.../traffic-management/Pages/Bank-On-Safety.aspx
I can't find it now, but I believe there's a map comparing where the pedestrian crossings are with where people
actually walk across the road. It shows that the number of people using the crossings is really quite small.