Look at the result, the possible causes and the desired outcome. Two aircraft collide in possible IMC whilst conducting IFR training. Both aircraft are OCTA, class G in the vicinity of a CTAF. It would appear that both are on area frequency and communicating with ATC. One aircraft has maintained an altitude for the previous 30 seconds which indicates a separation standard was in progress. Without blame, what would have resulted in the best outcome of four good people still being with us today? Both pilots given and maintain an altitude till verified passage? Both pilots receiving positive vectoring? One or both pilots having , at least, an operational real time ADS-B Rx unit (certified or not)? Or, one pilot held on the ground till the incoming aircraft is visual? Class G obviously only works in VMC.
IFR pays for a service in Class E and above. Could this be amended to allow a service, even in Class G, if there is reliable spacial traffic information? THE desired outcome is a separation standard in IMC in ALL airspace within the ADS-B coverage map.
EDIT to add- This entire incident would be expected to recorded in high fidelity from the raw 1090ES stream...wouldn't it? If not, why not?