I have a automatic 2015 Scion tC RS9.
I think Scion / Toyota considers that a "Lifetime Fluid". I have both the Original Owners Manual and the Warranty / Maintenance Guide.
It shows the Recommended Service all the way up to 120,000 miles or 144 months.
There is No Recommended Auto Transmission Service Interval for that time span for Normal Service. Now, I only have 25k on my RS9
so I don't anticipate any problems with my transmission anytime soon.
This Subject was Previously discussed here:
Scion tC 2011-2016 Automatic Transmission Fluid Change