I'd do my best to avoid making matters worse, and within my own sphere of action and influence, I'd do my best to encourage collaboration with those on the other sides of silo walls, but that's about it -- unless I decided to leave for a better environment. Otherwise I'd stick to my knitting while keeping my nose clean.
Anyway, trying to fix this would mean traversing too many management layers and overcoming too many commitments by managers and executives who stand to lose a great deal if they end up having to admit they were wrong.
If I was put in charge of the mess? That's a different matter. As I said in my column on the subject, the keys are alignment and collaboration.
With respect to alignment, I'd take a hard look at how everyone in my organization is compensated, and in particular what sorts of behavior lead to the highest compensation. I'd adjust this so that a significant component of at-risk pay (read: bonuses) depends on all parties trusting each other, working together well, and keeping each other in the loop.
This isn't a matter of bribing employees to do the right thing. It's a matter of compensation being the organization's loudest voice -- the one that speaks the truth about what the company values. I'd want my loudest voice to broadcast my desire for everyone to be shooting at the same target.
Along with compensation, I'd look at the communications environment and make sure every possible tool is in place to reduce the impact of geographic separation. More than that, I'd ensure everyone receives so much training and support in the use of these tools that they become second nature, so they facilitate collaboration instead of serving as a distraction.
Collaboration: This is a matter of structuring projects and goals so that teamwork is required for success. If anyone has important goals that put them in competition with their peers, I'd ask to be told about this so that I could fix it -- competing goals are one of the most pernicious sources of silo-style behavior.
That's a start, at least. There's a lot more, especially on the culture front. But to fix the culture, you have to fix leader behavior, and to fix leader behavior you have to build alignment and collaboration -- if, of course, you're in a position to do so.