Try putting some can catfood near the pallets,everyday,they will see you,and start coming once they get used to hearing the can opening.
The best way that I know of is by using food and trying to have them come over to you. As well as being quiet, moving very slowly, and have a lot of patience.
Maybe set up a trap ?
This site is for SPCA inquiries only. Sorry, maybe try contacting animal control or the actual SPCA shelter for them to find a way to pick up the cats.
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