Yes, a user can use the same wildcard SSL Certificate with the same CSR and Private Key on different IP addresses and physical servers.
The limits on the number of physical servers and IP addresses you may use your certificate on depends on the Certificate Authority.
Certificate Authorities like Comodo, GeoTrust, RapidSSL, and Thawte offer wildcard SSL certificates with an unlimited server license policy. So, the customer does not need to face any hassle when installing a wildcard SSL certificate on multiple IP addresses and physical servers.
If you go with a Symantec Wildcard SSL Certificate, you are limited to a single server license. That means if you wish to use the certificate on another server or IP address, you need to purchase one more server license from Symantec.