I'm seeing this 60 day special offer in Google Play on my phone - but not on the play store on my computer browser, which is showing the usual 30 day trial. (So the url in this post doesn't point to the special offer. You may also find it on your phone). I can't see any information about when the trial starts and ends. $11.99 pm thereafter as per usual. You probably need to cancel your subscription before the free trial ends to avoid it automatically rolling into the paid service after the trial.
I may give it a go but don't think I'll use the paid version. I use Plex with Plexpass to access all the music I own and Spotify (add-supported) to listen to new music / radio mixes. Happy to buy and own new music rather than paying a monthly fee to listen to, but never own it - which means you lose any music you haven't purchased if you end your subscription.
It looks like its only available to users who haven't used a free trial or who aren't existing all access users.
Can be a bit more specific where the offer is listed? I have Player installed and that's all I can see on Google Play?