How susceptible is 802.11n to other 802.11x networks?
We are looking to use Cisco's 802.11n in a new building, However it's going to be multiple tenant facility and multiple 802.11x networks may become present.
Is there good documentation on issues with interference and 802.11n that someone could provide?
In terms of interference ... 802.11n operating in the 2.4 GHz 20MHz spectrum will suffer from the same interference as 802.11b/g ... if you enable the 40 MHz channel bonding then the interference will likely get worst because of that will decrease the 3 overlapping channels to just 1 channel therefore co-channel interference will be seen immediately.
With that said, if you are designing a mutli-tennant building for 802.11n, I would start by utilizing the 5GHz spectrum because its cleaner and you'll be able to use channel bonding or the 40 MHz band to increase the speed and bandwidth of the overall WLAN.
I have attached a design guide for your review ... hopefully this helps you in your efforts.