It takes a really good Expensive soldering iron or really really good one. even then the entire pickup gets extremely hot. The wax potting will melt.
I've removed pickup covers three times now, the second two times I've used an extremely brand-new ultra sharp razor blade Utility knife works well,
much safer for the pickup, if you do it very slowly and cut very close to the edge of the cover, Once you've cut about cut about halfway The last little piece of solder just breaks away from the cover. Just be careful not to stick the knife into the wound portion of the pickups.
I much prefer the uncovered tone.