Is it possible to use segment.io with one classic google analytics tracking code concurrently with an extra universal google analytics tracking code(not integrated in segment.io) on the same page?
Thank you,
Yep, absolutely. Classic GA loads their ga.js library, whereas Universal GA loads their analytics.js library.
You can load Universal inside Segment.io just be adding your universal UA-code into Segment.io, and then leave the old ga.js tag's in place as-is. Or at least that's probably the most straight-forward transition plan :)