Naval News reports that the French Navy is testing a containerized Thales CAPTAS-1 active/passive variable depth sonar (VDS).
This not the only such sonar available. The Canadians offer a similar system.
Should it be necessary, such systems could conceivably allow sonar systems to be added to all Coast Guard cutters the size of the Webber class Fast Response Cutters and larger.
Chuck Hill's CG Blog 
I don’t know. These sort of things get the masses on defence blogs and forums very excited. Put it in a container and they think they can install them on anything.
All I will say is a small set installed on small platform whose propulsion system is not rafted will struggle; especially in difficult environments like the littoral.
I could be wrong.
They tested the VDS/MFTA combo for LCS off the back of a 150′ fast supply vessel.
I know it has been tested. One still isn’t convinced. 😉
Certainly it needs to be tied into the ships command and communications system. It is not as easy as just placing it on any available deck.
Does any Western country have a containerised VDS in service?
Any reports on them in service?
Some have been tested, but I am not aware of any that are currently deployed.
It is not surprising in that if you are building an ASW ship you have and installed sonar.
Containerized sonars would be for mobilization but even then, you have the option of upgrading the ship with an installed system if you have the time.
Containerized systems would make sense for a mobilization scheme where the Navy maintained containerized systems that could be manned by reservists and quickly installed on non-navy ships like cutters because it would not be necessary for the Coast Guard to maintain and man the systems prior to mobilization.