As touchy as the Adobe update process is about not finding exactly what it expects, and as certain as updates are with the cloud model...
Are you sure you want to be hacking into Adobe's installed files?
The only splash screen that i was able to edit was the Illustrator one, because the raw files were in the Windows folder. I have also tried looking in the PSArt.dll for the encrypted versions, but without any luck.
The updater process shouldn't remove the custom ones, because I just replaced the new ones with the same file names.
Rather than add your company name directly to a product splash screen that your company had no part in creating, how about a little batch script that puts up your company logo before launching Photoshop? It's not something I would know how to do, but from the little scripts you find in the installation process of aplication DVDs, I suspect it is not hard to do. Are you a Mac or PC kind of a guy?
Powershell may be the way to go then, as it can access the .net libraries and can run batch files, etc. You could download the free version of visual studio and use the form editor and use it to create a splash screen. Then run a batch that loads it before photoshop.
So there are some options. powershell scripting maybe disabled on your system for security reasons, If you have an IT guy, you may need to ask him about it.