IMHO, it would be very helpful if the Property task could get its properties via a url, e.g., http://devwebsite/projects/common/build.properties (I suppose there is almost no limit of useful sources from which a Property task could draw its data, but this seems pretty straight forward) also IMHO, it would be useful if an ant file could include another antfile elsewhere on the network via url.
Also, a satisfactory workaround would be to use the <get> task to pull the contents of a URL to a local file and then use it with <property> or <ant>.
Allowing for URLs all the way throughtout will provide the means for things like: ant -u http://devwebsite/projects/common/build.xml -Dbasedir=. where -u is like -f but for URLs. And this would allow to have build file that do everything including getting the source using CVS.
property has supported the url attribute since 1.6.0 . modifying description. Ant is close as well.
Loading the buildfile from URL is difficult because of the basedir. That's discussed on the dev-list. "include another antfile" would be done via <import>. That doesnt handle URLs (or ResourceCollections). I think because of the same reasons (import sets a property to that directory).