What would be the drivers for this dichotomy? Why are two different messaging systems necessary? What would limit AMQP from being used on the internet scale? What would limit XMPP from being used on the intranet scale?
Patrick may well be right — I don’t know enough about either AMQP or XMPP to credibly defend my gut feeling. One of my motivations, though, was that XMPP is based on XML, while AMQP (AFAIK) is binary. This suggests to me that AMQP will probably outperform XMPP for any given scenario — at the cost of interoperability (e.g. with regard to i18n). So AMQP might be a better choice if you control both ends of the wire (in this case, both ends of the message queue), while XMPP might be better to support looser coupling.
But as I keep saying (after hearing something similar from Mark Baker for years): most of the stuff that works on Internet scale is a better choice for company-internal scenarios, too — so I’m aware I may be slightly contradicting myself here.