Filtering is illegal in France, the trial allowed filtering on dual carriageways with a speed limit of 70 km/h or greater in eleven départements, which included those of Île-de-France in addition to those Rusty99 names.
The result was a significant increase in accidents in Gironde (54% on the trial roads compared to a 28% reduction in accidents on other roads in the département), but a slight increase elsewhere (a 10% increase against a background of a 9% reduction in the other ten départements).
4,500 total accidents were recorded on the trial roads during the testing period of 2015–18, of which those involving filtering consisted of 1,650 minor accidents, 161 serious accidents, and 16 fatal accidents. None of the riders involved in the fatal accidents were riding legally. Some ignored the requirements on positioning, but most were travelling faster than the trial’s 50 km/h limit for filtering speed.
As the purpose of the trial was to reduce accidents, the results were unconsidered unclear so a change will not be adopted. However refinements for further trials could be considered, which could include better education for all road users.
All of which is notwithstanding how well the law was already being followed anyway.
If you read French, the full report is here: