The intention is to protect the iron hub from corroding and seizing the sensor into its hole. Mine have all been fine with Action Can CS-90 but red grease might make more sense.
A neodymium magnet drops slowly down a copper pipe because the relative movement creates electrical eddy currents in the copper which resist the fall of the magnet. Non moving copper grains in a grease wont have any electrical effect.
sorry if it sounds like a get at Dave which is not my intention,
take a look on the 911 forms there's shed loads some photos of accelerated corrosion due to copper anti seize.
take a look on boat forums
GM have posted a bulletin about corrosion on there trucks lifting the abs causing them not to work, they specify mineral grease for some reason
don't take my word for it became enough of a problem for manufacture to specify that copper grease shouldn't be used for this application and some such as Mitsubishi void warranties if it has been used
personally I don't own any, its known to cause stainless steel to crack., transfer heat and damage near by components, corrode aluminium if the solvent gets washed out, I can find loads of evidence of it causing problems, I can not find any as to why it should be used in this application. Great on hot dry steel.
here is what a supplier says, I could post a link but this is just a straight copy and past
Anti seize compounds such as copper grease are an anti-seize compound and not a lubricant. Copper grease is also conductive and contains solid particles. Should it contaminate the ABS sensors it could interfere with the ABS signals. Copper grease is not suitable for the brake environment as a galvanic reaction is likely to occur. Galvanic corrosion is caused due to 2 dissimilar metals reacting with each other. All metals have galvanic qualities. This is a measure of a metal’s resistance to corrosion when in contact with another metal. A greater relative diff erence in galvanic quality between the two metals in contact indicates a greater corrosion potential. Galvanic corrosion (also called bimetallic corrosion) is an electrochemical process in which one metal corrodes preferentially to another when both metals are in electrical contact, in the presence of an electrolyte. Since copper has one of the highest galvanic numbers or nobility of the active metals, it will not be harmed by contact with any of them. It will, however, cause corrosion of the other metals if in direct contact. Thus preventing the pad from moving freely in the caliper/ carrier. The electrolyte may be rain water or moisture from the air containing enough acid to cause it to act as an electrolyte. This results in the deterioration of the metal with the lower galvanic number. Contact in a saline environment or salty water will accelerate corrosion.