Consensus for its implementation was not established within a reasonable period of time. If you want to revive discussion, please use the talk page or initiate a thread at the village pump.
Any editor can request probationary (trial) adminship, if the editor can find a serving administrator who is willing to endorse the editor's application and mentor the applicant during the probationary adminship. Enthusiasm is what counts, not editcountitis.
Probation of an endorsed candidate will be discussed for a few days and is passed unless there are compelling reasons not to based on the user's past deeds. Speculative reasoning, and "lack of participation in process X" are explicitly not good reasons.
A bureaucrat makes the decision as to whether "compelling reasons" have been raised or not. If the mentor has been an admin for only a short time, or is already mentoring someone else, the bureaucrats may require the candidate to find another mentor.
Probation lasts one month. At that point, the user gets regular adminship unless (1) at least ten regular users object to that, in which case a regular RFA decides, or (2) the user has barely used the tools at all (as judged by the mentor), in which case the editor probably doesn't need them.
Trial admin status can be revoked instantly by the mentor, or by any bureaucrat who considers that necessary. (Yes, I know they can't demote technically, but they get to make the decision; other users get to convince the 'crat.)
An editor can only become a trial administrator once. Thereafter, adminship must be through a regular RfA. An editor who has already had an unsuccessful RFA is not eligible for a trial.