Wavelab 8 excels at metadata, ISRC, CD-Text and UPC, but it won't be until Wavelab 8.5.20 due out later this summer that the ISRC embedding to WAV files will comply with the new standard. Wavelab can currently embed ISRC codes into rendered WAV files but in a way that pretty much only Wavelab can read. Soon it will be inline with the standard that is being proposed.
The "standard" for embedding ISRC codes into WAV files is still fairly new:
The Music Producers Guild | | ISRC / BWAV press
The most simple app for adding ISRC codes to WAV files using the new standard is Sonoris ISRC Editor:
ISRC Editor - Sonoris Audio Engineering
It's a free app, but it doesn't do any other metadata though. If you need an all-in-one solution today, the Sonoris and HOFA products are current with the new ISRC standard. Both HOFA and Sonoris have DDP Creation apps that will let you enter in CD-Text, ISRC, and UPC for the entire album.
What happens to the ISRC codes and other metadata when the WAVs are converted to mp3 is dependent on how it's done, but I wouldn't count on it all translating.
Jaikoz is a great app if you also need to supply mp3 versions with full metadata and ISRC codes.
To answer a previous question, the mastering engineer can either work with ISRC codes provided by the client, or the mastering engineer can sign up to be an ISRC manager with ISRC and have the ability (for a yearly fee) to assign codes to clients that need them.
I only assign codes when asked or they are provided by the client.