I just logged on to PTR with two of my shamans to do a quick test:

NO mods enabled, NO talent points assigned, NO buffs, NO glyphs.

Shaman1 by himself (1750 spell dmg): healing stream is 150/tick
Shaman2 by himself (2050 spell dmg): healing stream is 193/tick

When I group the two of them together in the same party, they BOTH get stacking healing stream totems effects in combat log and in portrait window.
When I turn it into a raid, they BOTH get stacking healing stream totem effects if in same party.
When I move the shamans into different parties in the raid, the healing stream totems do NOT stack anymore.

In essence, healing stream on PTR currently is unchanged completely from 3.09. Its a party-only buff and stacks. They may not be done fiddling with it though and I would guess they turn it into a raid-wide, non stacking totem before 3.1 goes live. However, at this time on PTR it is exactly the same as it is live.

back to leveling my DK now, we'll see how totems change on PTR in upcoming weeks.