Yes, it is possible.
Need a File Manager w/Root
First, you need a file manager that has root access. Personally I use ES File Explorer. Within ES File Explorer, you will need to enable Root access (it's under the Tools part on the left menu).
All users will need to have signed in
All users must have had to signin at least once to create their partitions. Else, you won't see them.
The exact location is:
/storage/emulated/* # Android <= 4.4.3
/mnt/shell/emulated/* # Android >= 4.4.4 (actually, it may be 4.4.3 too)
* is the userid. I am not sure how to get the user ID, but on my tablets with 3 users it shows up as:
/mnt/shell/emulated/0 # owner account
/mnt/shell/emulated/10 # first user I created
/mnt/shell/emulated/11 # second user I created
From what I gather for userids, it goes in order that I created the users. 0 = the first original owner account. Then each account goes up from there (10, 11, 12, etc).
NOTE: If your file manager does NOT have root permissions (meaning the app itself must request root access), then when you enter one of the directories above, they will be blank. This is telling you that your file manager doesn't have root access - you need a file manager that knows how to request Root access.