http://www.bfes.ea.com/news.read.asp?id=3604
The Comunidad de Battlefield España website is showing the server requirements for Battlefield 2. As far as how accurate this information is only time will tell.
Linux:
Minimum specifications for 16 players - Processor: 1.0 GHz and Memory: 256 MB RAM
Recommended specifications for 64 players - Processor: Intel Pentium IV or Athlon XP 3.0 GHz or Opteron 64-bit 1.8 GHz and Memory: 1 GB RAM
Windows:
Minimum specifications for 16 players - Processor: 1.0 GHz and Memory: 384 MB RAM
Recommended specifications for 64 players - Processor: Intel Pentium IV or Athlon XP 3.0 GHz and Memory: 1 GB RAM
Bandwidth: 2.5 Mbit. Recomended: 5 Mbit