Do you have a dedicated server? If yes, then you're probably free to run Jabber from a server standpoint. If not, and you're just a web hosting client, you'll definitely
need to seek a prospective host's approval (and you can often expect to pay a little extra per month).
From a network standpoint, IRC has a reputation for frequent DoS attacks by chat users -- and is often banned for that reason. Whether Jabber would be allowed on the network would probably depend on the audience scope and size. (Internal company users? Random public users? Just a few users, or many users?)
You may find this useful from the Jabber wiki:
<---- Lists some Jabber hosts
The wiki indicates that DreamHost offers free Jabber server hosting on its web hosting accounts. That may be the best way for you to go.