The service puts the lie to concerns that incumbent telcos would squash IP-Telephony in an effort to preserve traditional toll charges. It recognizes that multinational, multi-site companies have huge financial incentives to avoid paying the tolls and taxes associated with international calls (just like individuals have been doing for years, using Skype, Fring, Truephone or other VoIP carriers).

In addition to cost savings, BT markets OneVoice Ribbit 1.0 as a feature-rich single-number service. Each user will have a single “direct dial number” that is associated with multiple phone lines. Most commonly the list will include that person’s business line, wireless phone, residential phone or a “softphone” in Web browser. Users can designate which phones should be involved for both inbound and outbound call handling.

As for the features and functions that should be important to corporate customers. Phones (endpoints) can be added or changed by users through a Web site. In addition, there are a number of (now) time-tested features that employees will find attractive, including the ability to view call logs and manage voicemail, which includes voicemail-to-text transcriptions. Transcribed messages are delivered a text to either an email address or a mobile phone in the form of SMS. In both cases, the message includes a way to listen to the original message, in the very likely instance that transcriptions contain errors or are hard to decipher. The full list of features is available here.

BT acquired Ribbit for $105 million in July of 2008. It was an act of faith and courage bolstered by confidence that the parent company could harness the creativity of a generation of developers whose sensibilities were not borne out of the Bell System. As the list of features and functions indicate, the Ribbit crew realized early on that phones could do more, and they focused on what the old guard (like me) would call “single number/find me-follow me” offerings.

With a rich set of tools for Web services development and a general trend toward moving all sorts of media streams and activity streams into the cloud, Ribbit’s biggest challenge was to narrow the set of offerings to services that individuals would use frequently in the office, at home and in between. In this respect it is often compared to Google Voice, but the affiliation with BT and the incorporation into OneVoice means that BT’s technical salesforce can bring a BT branded solution to its customer base. That should be a clear advantage over Google, but only time will tell.

The phrase “over-the-top” suggests a level of extravagance (think of “over the top” entertainment). Yet, during the past 10 years it has become synonymous with “cheap international calls”. In 2010, I expect OTT to return to form and refer to all sorts of value-added services and innovations, whose providers take advantage of those “cheap” or “free” minutes to take VoIP “beyond customary boundaries” (which happens to be one of the Dictionary.com definitions for “over the top”). Avaya and 02 are seeing the same trend, and we can expect a stream of acquisitions, partnerships and innovative service offerings that take incumbent carriers and traditional enterprise infrastructure providers over-the-top and outside their comfort zone. Case in point: BT with Ribbit.

“Unified Communications” (UC) figures prominently in this service offering. BT brands its offering the “OneVoice UCC portfolio” and Cisco calls it the virtualization of its Unified Communications Manager infrastructure. But that is just the beginning. Nonetheless, what we are witnessing these days on an enterprise-by-enterprise level is less about unification of communications and more about assembling or re-assembling solutions that serve specific needs – within enterprises, among multiple enterprises and between enterprises and their customers.

The business details of the agreement were not made public, but the two companies have worked together since 2000. This week’s announcement represents an effort to expand from a base of current users in the UK initially into the U.S. and Europe today, the Middle East and Africa next year, followed by Asian-Pacific countries.