I would still right a letter to your local "wildlife and forestry commision" (I think thats the name of the yanks version of the UK DEFRA) before proceeding just in case, better to be covered by a large government supported organisation in case legal proceedings occur then on your own, It may take a while to get but keep pestering them just in case. Koi are best caught with netting on a warm summers evening around dusk prefferably, tinned tuna should bring them to the area quitequickly to be netted. I can see why you may not have the patience for net so any anglers advice for catching carp should work well, as they are essentially selectively bred carp. To transport is difficult I would think a bin lined with bin liners which have been soaked and washed thoroughly with just water filled to 3/4 full would be best for transporting large quantities of fish safely. They then need to be house in a pond atleast 6 feet deep and prefferably 10 foot long 6 foot wide although smaller temporary enclosures can be used. Pretty much any local fish shop will jump on the chance for koi as they sell for big money hence why I was apprehensive to advise you earlier. Good quality show carp sell for $5000+ but if these were released by a local they will still be aroud $40+ a piece which although their is a recession I find very strange for someone to simply chuck away.