Amid all the hoopla about dual-mode phones, both in the consumer & enterprise markets, it's easy to forget that there's also a parallel stream of work going on to integrate corporate telephony better with "plain old" mobile, especially where devices can accommodate an enterprise-centric software client.
Avaya's been talking up its mobile extension product for some time, which is available now on Symbian handsets, with a Windows version looking likely as well. And I noticed that Cisco acquired Orative yesterday for $31m, which has solutions for Symbian, BlackBerry and interestingly also Qualcomm's BREW. Furthermore, a briefing with BroadSoft (more focused on operator-hosted Centrex) highlighted its own client as well, and I just noticed from OnRelay's website that they did a deal with Siemens in the summer too.
The only downside with some of these solutions is that it may generate an extra call leg between handset & PBX - but given the increasing desperation of operators to win corporate business, that incremental cost is falling rapidly.
Add in the private cellular model emerging in the UK from players like PMN, and you get a picture of two converging world - albeit slowly - as PBXs and cellphones start to work together a bit more collaboratively.