IOS – “Hey Siri” doesn’t run if iPad locked and Smart Cover Closed in iOS 11

According to the Smart Cover page on the Apple store:

The iPad Smart Cover is compatible with iPad 2 or later.

Also at the bottom of the page:

So, the answer, based what Apple has said, is yes, the original Smart Cover will fit both the iPad 2 and the iPad 3.

There are also several questions linked in the product page that say that the cover will fit.

Edit 9/1/12:
I did mean to update this when I found the link, but I lost it for a time and recently found it again.

According to a MacRumors report on March 22nd, some people did (and presumably still are) have some trouble with the magnets on the iPad 3. According to Marc Booth, Apple changed the polarity of the magnets sometime in 2011, because "some iPad 2 customers were having issues with their iPads entering sleep mode when they flipped Apple's Smart Cover around flat behind their iPad 2". Marc also reports that "Apple is replacing older Apple Smart Covers at Apple Stores for customers who ask."

The short answer is no, not yet. The long answer is because the only (reliable/legal) way to get Siri on a non-iPhone 4S device is to use a package found in Cydia called Spire. This requires you to have access to a Siri proxy server or an iPhone 4S for the tokens. However, @chpwn (the developer of the package) has stated many times that it will not run on iOS 5.1, because the iPhone 4S IPSW (the actual firmware downloaded from Apple) cannot be unencrypted at this time. This IPSW is needed to harvest the Siri files for use on other devices. He could port it illegally, but he doesn't plan on it. Because the new iPad is running iOS 5.1, Siri cannot be run on it, plus a public JailBreak for the new iPad hasn't been released yet.