According to this guide you are at least required to provide the IMEI of a "AT&T compatible netbook/laptop" listed
here upon registration/activation of your SIM (which you have to perform online at
http://www.att.com/buyasession). I don't know if they actually check your device being "AT&T approved" or if this is rather a recommendation but once registered I guess the SIM is tied to the registered device. The answer to your question costs $ 4.28 - that's the price of a AT&T SIM including delivery to Europe, which you could try to register through
http://www.att.com/buyasession while providing the IMEI of your own device.