Ick will not bother inverts. Also, don't plan on that shrimp being able to "cure" or rid any fish of ick. Medications, mostly copper based or hyposalinity treatments are best bets. Copper will render the tank unable to ever have inverts again though. They can't do copper and it stays in the tank even though not treating any longer.
But, until you ever have to treat, the shrimp will be fine there.
"Life may not be the party we hoped for but while we are here we might as well dance!"