Two aspects regarding Digital tower implementation:
1. Rules / Regulations - i.e. the rule for reduced separation in the vicinity of an aerodrome - ATCO has both aircraft in sight. Now an electronic device is to be used and not glass windows. EASA has already looked at some words to try and manage this change, ICAO is doing the same but with a different approach, but does any electronic display method, with or without additional tools, equate to the same as glass windows? Maybe a bigger question, if electronic tools are added to the "visual" can the ATCO use those added tools to provide reduced separation? (As Gonzo showed a potential usage in post #133) We already have pilots reporting when asked to report visual with other traffic - "I see him on my TCAS!"
2. Complexity - So we presently have glass windows (needs cleaning occasionally) and the controller's eyeball.
Digital towers - LCY glass window is to be replaced with 14 fixed cameras and 2 mobile cameras with power sources - computer / data transfer to another location - computers / data retrieval at this new location / display methods at new location (14 for a 360 by the looks of it). All of these have points of failure in them, so increase risks. Anyone who has worked with ATC simulators my appreciate how often display devices can have issues or fail. All of this to replace the simple glass window, without any fancy add on tools, before the controller's eyeball. Sounds like an increased risk of failure to me - lots of expensive mitigation measures required to reduce the risk, yet still the possibility exists. Unfortunately the long term costs of all this added electronic and mechanical complexity still appears to be less than either land or staff costs.
I would have rather seen money spent on an "augmented reality" idea of Google Glass be introduced into existing towers - with all these useful digital tower tools to be as overlays to supplement the ATCOs safety, whilst not changing the window view - but all of this would have just been extra cost, therefore not so interesting to people interested in saving money.
LCY have specific ideas for the land that the normal glass tower takes up, so they want this to happen. Other areas of the world have introduced remote towers to specifically to reduce staff costs at remote / quiet airfields. However I understand that Dubai World Central was looking at digital towers for when more runways were to be built - looking to be the first "Tower-less" airport in the world!!
Can we stop it happening, probably not. Should we raise every safety concern we have, based on our experience - absolutely. But views of risks will vary from ATCO to ATCO, so some see this as a great step forwards, whilst others are more cautious or even anti.
It all sounds great if all this added complexity works - time will tell. Just maybe not so good for our working terms and conditions in the long run.