Can they?  Yes.  But it's not automatic.

Jon Skeet wrote (is writing?) an article on the topic, which you can find  
here:
http://msmvps.com/blogs/jon.skeet/archive/2007/11/20/vs2005-and-vs2008-co-existe
nce.aspx

There are limitations to just how much sharing between VS versions you can  
do.  It's definitely not completely seamless.  But you can manage if it's  
important enough.

Pete

The main thing is that your app must not target anything above the 2.0
Framework level. You'll need to keep two versions of the solution (.sln) file
as these aren't compatible, although changing them with a text editor is
simple enough.
-- Peter
Site: http://www.eggheadcafe.com
UnBlog: http://petesbloggerama.blogspot.com
Short Urls & more: http://ittyurl.net

Don't be the renegade.  Talk with your team about all switching or else none
switching.  Doing something independant as this is not good for the team.

That said, if each is tasked with one or more independant DLL/executable
projects, the it should be fine.

I handled this by having projects of different names. For example The
original project was made in VS2003 and named ProjectVS7. When we
Upgraded to VS2005 I copied the project and renamed it to ProjectVS8. I
then ran VS2005 and converted that one. When we upgraded to VS2008 I
copied it and named it ProjectVS9 and converted that. Now we have 3
projects that work with all three versions of Visual Studio.

Hope this helps.
Leon Lambert