Despite explanations offered by IRCC (typically by help line agents) and MPs and others, USUALLY (not always) the progress of a citizenship application through the process is NOT held up by background checks.
Some Clarifications:
There are three formal "background" checks:
-- GCMS (done repeatedly throughout the entire process); includes so-called "immigration" checks as well as name-record criminality checks; done by IRCC processing agents and the Citizenship Officer who makes final decision
-- RCMP criminality check; done by RCMP pursuant to referral from IRCC, initially by referral from CPC-Sydney but sometimes there is an update referral from a local office
-- CSIS security check; done by by RCMP pursuant to referral from IRCC, initially by referral from CPC-Sydney but sometimes there is an update referral from a local office (rarely results in delaying application processing UNLESS, for this or that reason, it involves a referral to overseas office for further investigation or there is otherwise an active investigation regarding the particular individual -- as best we can discern, this is rare or at least NOT at all common)
Further Related Observations (about these checks):
Beyond the fact of referral, very little information about the background checks is public, and is among the most closely held confidential information kept more or less secret by the government; most of what actually happens, both substantively and procedurally, is done behind closed curtains behind closed doors.
CSIS security check is done pursuant to referral from the CPC-Sydney attendant the very first actions taken on an application once it is "accepted" as complete. Referral to RCMP for its criminal check is made at the same time.
For the vast majority of applicants these referrals result in the respective clearance before the local office takes action on the file (usual first action by local office is test/interview preparation).
It appears that sometimes there are follow-up referrals to update one or the other, or both the CSIS and RCMP checks. Even if this is done, for most applicants (by a big margin) this does not result in a delay or not much of a delay.
It appears that applicants are often advised, in response to queries about the status of their application, this or that background check is pending. This is technically true on the face of the file, since the background check is not deemed complete until the responsible officer reviews and makes an entry into the file in effect checking off the clearance is complete. MOST (not all) the time the clearance itself has been received. This is comparable to when the application itself arrives at CPC-Sydney but IRCC does not acknowledge receipt for many weeks, sometimes several months (difference in time between application delivered to Sydney and AOR). During this period of time the application is in fact in Sydney, but there is nothing in IRCC records which show that. Similarly, the RCMP and CSIS clearance has been submitted by the respective agency, but IRCC has, in effect, not yet acknowledged its receipt. So, GCMS does not show the clearances as complete, even though the checks most likely have in fact been done. So, help line telephone agents will often say to clients that the background checks are still pending, even though the checks most likely have in fact been done.
In other words, while in effect there is no acknowledgement of receipt of the security or criminal checks, it is NOT as if the application is waiting for them to be received. That is, there is rarely any delay due to outstanding security or criminality checks. The checks are done but without acknowledgement they are done.
CAVEAT: of course there are outstanding checks for some applicants, and for this or that very individual-specific reason the agency has not provided the clearance. Applicants affected by this will usually, almost always, have some idea this could be a problem because it almost always relates to that individual's actual history.
IN THE MEANTIME, IRCC repeatedly conducts the GCMS background clearance attendant every action taken on the file. This includes at least name-record criminality screening (which includes screening name-record databases derived from RCMP and U.S. NCIC/FBI databases). And this check, while done and done multiple times, remains outstanding right up to the last action taken prior to the oath ceremony. This means that technically "background checks" remain pending right up to the very end . . . so, a help line telephone agent can always truthfully say background checks are pending, even though that has nothing at all to do with why the file has not moved on to the next step.