I'm not a hundred percent sure, but I think the original BMW cables were Teflon coated and lubrication culdcause swelling of the coating and could therefore worsen the situation.
Maybe some of the other guys can verify this...

That's correct. The lining is of a certain material that swells if it gets in contact with certain liquids (nicely vagely put) I think Silicone grease is OK, but am not certain.