How did Pakistan manage to integrate SLCM with SUBTICS without OEM consent? That's a move that would blow any End-User clause/support agreement out of the water!
They don't need to be integrated into SUBTICS. Torpedoes do because they remain in constant contact with the submarine's FCS and hardlinked to the submarine via control wires until autonomous tracking takes place within what could be considered terminal distance.
Norway is currently doing last-life upgrades on its Ula class submarines which includes FCS mods to make them able to handle newer generations of torpedoes.
The submarines are also having JSM - called NSM-SL when sub-launched - integrated into them, though the missile while be featured on the Ula replacement, not the Ulas themselves. The Ulas will be used for test-launches.
Because they don't use any systems that would need to be hard-linked with a submarine's FCS, and can be launched using the same protocols that see any foreign object evacuated from the torpedo tubes, such as MJK commandoes, the JSM can be launched regardless of any mods to the submarines systems.
Using strictly passive forms of guidance, they need minimal contact with the submarine itself.
Most SLCMs have their own control systems like Tomahawk's "Tactical Tomahawk Weapons Control System" that can be integrated into a boat's FCS to allow the missile to receive mid-course updates, but that's not strictly necessary.
It's still a good idea to integrate a missile into the greater FCS, which would require a modification of SUBTICS on French-origin submarines.
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I can tell you from professional experience that when we do integration for AUVs we do need to make mods if we're running a control wire to the submarine mothership. But for disposable, one-shot systems like Mine Sniper, no such thing needs to be done. Just flood the tubes and launch and let the AUV's active guidance do its work.
