Can a PEAR package rely on an external PHP script

I'm considering putting together a PEAR package for interacting with a web service. Conceivably there are two packages needed, one to handle authentication and a second to fetch the data. There is already a script available to handle the authentication but nothing available for fetching the data. Is it appropriate to rely on the existing script for authentication or should they both be PEAR scripts? The usage would be along the lines of: $auth = new externalClass; $credentials = $auth->processLogin($authVars); $data = new PEARClass; $results = $data->fetch($credentials); It would be possible to port the external class to a PEAR package but the specification is frustrating to work with and I would prefer to avoid this if possible. I can't see anything in the documentation which would prohibit this but I'm also unaware of any other packages doing similar. Cheers, Jonathan Street