Yes, FileUpEE upload resumability can be used in a web farm environment.

It is important to understand how FileUpEE resumability works. When resumability is turned on, both XFileEE on the client and the HttpModule on the server will keep track of each upload request, identified with a unique JobID. FileUpEE stores this information on the server in the same directory as the cached temp files. This location is defined in the FileUpEeTempDir key in the AppSettings section of your web.config file (see documentation). Therefore, if you are caching your files on the webserver there could be an issue if the user's request for resuming the upload is directed to a different server. That server wouldn't have the information about the previously interrupted request. There are two solutions:

1. Set the FileUpEeTempDir key to a UNC path for a network share with appropriate NTFS permissions (see this KB article). In this way, all web servers in the farm will have access to the resume information and temp files.
2. If you prefer to cache your temp files on the individual web servers, you will need to set your load balancer to use something like IP-based persistence ("sticky sessions") so that all requests from an individual user are directed to the same server.

Which of the above methods you should choose depends on the load of file transfers in your application. If you have a high-traffic site, but only a small portion of the requests are uploads, then caching to a network share is a good option. However, if your application is primarily being used for uploads, then the network share could become a bottleneck and "sticky sessions" may be a better option.