There is some debate going on about how to handle GA and ADS-B in Europe.
ADS-B is a distributed cooperative type of surveillance. This has its advantages and its risk. One of the risks is that (uncertified) installations transmit misleading data, which could lead to misidentification, loss of separation or worse. Therefor it is undesirable that GA is equipped with uncertified ADS-B transponders. At this moment there is a lack of certification standards for GA type aircraft. Also the technical standards are aimed at transport aircraft. Low power transponders or pure ADS-B transmitters are not yet standardised.
I don't expect Europe to go down the US route and have 2 separate and incompatible ADS-B systems. If GA in Europe is going to be ADS-B equipped, it will be on 1090ES so that everybody is visible to everybody.
To experience full benefits of ADS-B, everyone it the airspace must be equipped with ADS-B so everyone can see each other on a traffic display.
What to do? Mandate everybody to have ADS-B out including GA. Close down parts of the airspace for non-ADS-B aircraft?
In short, it's not very straight forward, and there are many decisions to be made. I don't see ADS-B mandated in Europe for GA very soon.
Although the rest of this post is a bit beside the OP's original question, I'll reply to some of the ADS-B related comments made here.
peterh337: I recall going to a Eurocontrol presentation in 2008 where they said they want to dismantle primary radars to save costs and replace them with ADS-B. These people live in their own world...
Primary radars are not likely to be replaced by ADS-B, they serve a different purpose (security). A number of Secondary and Mode S radars is likely to be replaced.
Denti: Interesting though that ADS-B out will be mandatory in less than three years for certain aircraft (more than 5,7t or 250kts cruise speed) within europe but the certification standards are not yet published.
ADS-B will be mandatory in European airspace for aircraft over 5.7t MTOM or 250 kts max cruise speed build after January 8th 2015. After December 7th 2017 all aircraft above 5.7t MTOM / 250Kts must be equipped. EASA is taking a long time getting the CS published indeed, but manufacturers seem to be aware of what will be required and are developing their systems.
Denti: the reason might be the issues around position data integrity which most if not all GA installation do not provide which means that ADS-B reports have to be discarded by ADS-B in systems anyway.
peterh337: Can you elaborate on why the data integrity is a problem?
Data integrity is one of the concerns for GA installations. GPS position can be calculated when a signal is received from 4 GPS satellites. If one of these signals is faulty (e.g. due to satellite orbit deviation, satellite failure, spoofing etc) the measured position will be off without the user knowing it. Therefor aviation receivers have RAIM, (Receiver Autonomous Integrity Monitoring) which requires at least 5 satellite signals. If all five (or more) signal are consistent with the same measured position, all is ok. If the signals are inconsistent a flag is raised and the position data is not to be trusted. The maximum horizontal position error that could go undetected by RAIM is the called the Horizontal Integrity Limit or containment radius. This is send out in the form of a quality indicator by ADS-B. If there is no integrity information available from GPS, the quality will be 0 and the position data is not trusted. The NMEA data format for example does not contain Horizontal Integrity Limit and therefor NMEA based GPS units are not suitable for certified ADS-B.
Rod1: All ADSB out via certified mode s transponders will have SIL enabled which will handle this.
SIL is Source Integrity Level (in 1090ES version 2) and indicates the robustness (probability of exceeding the containment radius without raising an alert) of the RAIM checks . It is one of the quality indicators that is transmitted, others being NIC (position integrity), NACp (position accuracy), SDA (system design assurance)
peterh337: The data integrity issue is nonsense. In all cases of Enhanced Mode S, the data comes from a collection of avionics boxes, including an airdata computer, and it is concentrated at the transponder. It either works or it doesn't.
There is a difference between data integrity and system integrity. Data integrity refers to undetected corruption in the original measurement (e.g. GPS position or pressure altitude). System integrity refers to corruption during the transport and processing of the data. You seem to be talking system integrity issues. Unfortunately it is not a case of "it either works or it doesn't", I have seen cases where misleading data was sent during a particular flight phase, which looked credible on first sight but was faulty on closer inspection.
mm_flynn: It will come as no surprise that the European implementation is scheduled further into the future
For aircraft above 5.7t MTOM / 250 KTAS Europe is ahead of the US. As said before, there is no schedule for GA.