William Brogden makes a meaningless point in a "REST vs. SOAP" post:

Another important, but frequently unappreciated point is that, in contrast with REST which requires HTTP, SOAP messages can be moved by any transport method which can handle Unicode text. Because of the convenience of HTTP for penetrating firewalls and the fact that developers are most familiar with the Web, HTTP transport continues to be emphasized.

I'd bet you could count on one hand (and use very few fingers doing it) finding all the non-HTTP uses of SOAP. On the vendor side, who actually supports that?