I've never seen any interference between strobe wiring and speaker wiring.
Crosstalk is Transformer Action
Crosstalk between wires is usually caused by transformer action. Transformer action is caused by one wire having varying electrical current (which causes a varying magnetic field), and other wire generating current because of the varying magnetic field.
This kind of crosstalk occurs very often, but usually is not a problem.
The interference shown in the article is generated in the Signaling Line Circuit (SLC). The SLC has a lot of varying current and is creating a varying magnetic field. Human ears are very sensitive, and the varying magnetic field generates a low-level varying current to flow in the speaker circuit. Even though this is a low-level signal for the crosstalk, it can be heard as it flows through the speakers. A constant magnetic field, however, does not generate any current in other wires.
Strobe Wiring to Speaker Wiring
The electrical current in strobe wiring is constant. It is either a constant, low current, non-varying current being used to supervise the wires, or it is a constant, high current, non-varying alarm current. In both conditions, the current is not creating varying magnetic field, so there is no crosstalk interference going from the strobe wiring to the speaker wiring.
Speaker Wiring to Strobe Wiring
Supervision current for the speaker wiring is not varying so when the speaker is turned off, there is no crosstalk from the speaker wiring. When the speaker is turned on, there is very low-level crosstalk that won't affect the strobes at all.