Nothing in this part shall have the effect of terminating any validly issued right-of-way or customary operation, maintenance, repair, and replacement activities of existing facilities issued, granted, or permitted to Molybdenum Corporation of America; Molycorp, Incorporated; or Union Oil Company of California (d/b/a Unocal Corporation); or its successors or assigns, or prohibiting renewal of such right-of-way, which is located on lands included in the Mojave National Preserve, but outside lands designated as wilderness under section
601
(a)(3). Such activities shall be conducted in a manner which will minimize the impact on preserve resources.