The month (or 30 day, to be precise) free trial will more than likely be granted when you first link ARR officially to your SE account. If you delay the link you'll probably delay the billing (and first /logon) I can't see it being a specific 30 day period only- It's a paid MMO standard to have 30 day sub included.
As stated above, Beta Phase 4 will have 1.XX characters available for use and the data from phase 4 will transfer to the release of 2.00. According to the roadmap the only benefit is: ( I see nothing in stone about Legacy members getting 30 days free, unless you are counting the beta)
Edited, Apr 15th 2013 8:16pm by deronguerra
- Version 1.0 service account holders will be able to download the commercial ARR client
free of charge.
* Those wishing to play on PlayStation®3 are required to purchase a copy of the game for