|Think about Loose Coupling|
nfsclient# mount -F nfs nfsserver.mydom.com:/sharedata01 /data01
on nfsserver.mydom.com there is a user entry in /etc/passwd that looks like this:
In this case the user has no access to login to the actual nfs server but the user and uid does exist and is matched from the nfs server and client. Quotas still apply.
I do no know what the setup is on the OP's network -- nor what the "Linux and Solaris don't talk" junk is about. What I would do is set up a cron on the nfs servers that runs a perl script that gets the output from repquota or vxrepquota and parses it then inserts it into a db server somewhere. The web app can then query the database and pull out the usage and quota info for the nfs server that is needed -- with no root level exposure to the nfs server.
PS Abigail-II: It makes sense to do the http request to machine A if the sysadmin wants to limit the scope of the end user. lets say I have 15 nfs mounts on 10 different servers exposed via CIFS/AFP/WEB on server A, I can show the quotas on different end user exposed directories without having the users know all of the details about the backend implementation. I do not know about you, but in my environment I can't expect end users to telnet to a machine and get quota info, much less to understand quota's and the backend implementation. I have to show them a nice interface that explains "hey silly, this you are at your size limit on this directory, please delete some stuff or call the helpdesk for more info!\n"; =)