PICAXE should work with XBee ZNet 2.5 though it wasn't clear to me from the manual whether the Programming Editor XBee Connect Wizard will allow them to be configured as required. Even if not, they will be configurable via Digi's / Maxstream's X-CTU and once configured should be usable just like XBee Series 1 as best I can tell.
The web site and user manual claim "No configuration necessary for out-of box RF communications" although that reads contrary to other parts of the user manual, so perhaps the Wizard will work even if not all options will be available.
I'd currently recommend people stick with XBee Series 1 for most projects a PICAXE is used with, but/and ...
Note: Products based on XBee ZNet 2.5 (formerly Series 2) modules do not communicate with products based on XBee 802.15.4 (formerly Series 1) modules.
Ho Hum. So much for across the board ZigBee "standardisation" and compatibility people were expecting.
Will that mean the obsoleting and discontinued production of Series 1 in the future ? If it does I imagine the XBee Wizard will have to be updated.
I doubt there's much more which can be said on using XBee ZNet 2.5 with PICAXE until someone has that experience under their belt. How complex or not configuration turns out to be is only going to be known when someone has had to do it. Hopefully that will also deliver simple instructions for others to follow.
According to the user manual and other press releases, XBee ZNet 2.5 hasn't had FCC etc approval yet so they may be hard to obtain except direct from Digi/Maxstream.