If you can get your company to fund it, there is a commercial version of Photosynth for local use under the banner of 'Geosynth'.
The other alternative is the recently announced Photosynth Commercial License.
This second option still involves uploading the photos here to Photosynth.net but you would have unlimited storage space for 'Unlisted' synths. The privacy works such that no search result anywhere on the site would link to your synth, nor should external search engines be able to catalogue them, however anyone that you gave a URL to could leak it on the web. Your company's need for privacy being what you describe, I have my doubts as to whether this second option is the one for you.