The way that projects drift down from on-high is, for me at least, one of the most frustrating things about project management. I'm not very good at simply doing what I am told. I like to know why a change should be made, what impact it will have, and what choices we can make which will optimize the business value for my host organization. In most cases it is not mine to wonder why, but simply to do or be asked to move on to the next client.
Still, I've discovered over the years that knowing the business problem we actually want to solve does improve our ability to deliver the "project". If we know that the organization needs X update to meet Y federal guideline with Z penalties we can structure our efforts one way, while if we know that the business problem we need to solve involves an organizational change coming in a few months (unbeknownst to the poor folks about to be managed out) we can tailor our communication plans accordingly.
If I cannot just get someone to tell me what is going on, I find one of the following techniques generally works reasonably well.
1) Take a long, hard look at a local business newspaper
It seems truly remarkable how much open intelligence you can gather about your own company by spending a few minutes either on-line (preferably not at work) or in a library reading local papers. Don't just look for your company's name - broaden your search to include the organization's officers, the company's various competitors, and logical allies.
Do not use this as an excuse to go talking to reporters about your company's inner workings. The object is to gather information, not spread rumors around.
2) Read your company's annual report (if it has one)
Amidst all the weasel words you can usually find information about things like "one-time loses", "incremental costs", and "operational expenses". You can bet that anything which cost the company money (and yes, that does include you and your department) came under scrutiny recently in an effort to make the organization more profitable.
Once you know what needs to be cut, you can begin to see the shape of what your organization wants you to really accomplish.
3) Pay attention to the "poverty pockets"
We all have projects which seem, to us anyway, to be terribly important but simply never get the funding they deserve. Products languish, business divisions suffer from neglect, and spreadsheets in programs that were out of support a decade ago run the business. These poverty pockets exist for a reason. Understanding who is served by their continued existence can shed a lot of light on how projects actually change, or fail to change, the environment.
Be careful with poverty pockets - they are often kept in place so that the anointed can perform heroic measures on an appropriate schedule.
Good luck and be careful. The powers-that-be sometimes do not like it when those of us who do catch site of their motives.