I think not every function provided by ETW is supported. For example, you can see from the remark of EventWrite() function that it's supported in Windows Phone 8, but some like OpenTrace() does not. So you should check every function you want to use before using them.

Since there are heavy lockdown in WP8 that only selected vendors have access to core system functions, I don't think the provider list is publicly available. However you may try your luck asking at Nokia/HTC/Samsung forum and see if someone would be able to tell you.