Shawls don't need to fit like a sweater so as long as the gauge isn't drastically different you're fine.
Answering your other post - you can usually find another substitute fingering yarn, here's some of the other yarns that were used. If you want to use laceweight instead that's fine. Lace is usually knit fairly loose so try out the needles suggested for the fingering weight and see how it looks, not so much to get the same gauge. Try a sample of the pattern repeat, or just cast on and work a few inches. Then block what you've got done, even while it's on the needles, and see how it looks. I see that it's done on a size 4 and that's not really too big for a lace yarn. If you want to go down in needle size that would be okay, you'll just need more yardage if you work more repeats of the pattern, or it may come out a little bit smaller.