Sum4all,
I can't speak for what 'TD' may be doing but my buying has been straight up personal buying through my TD account. I've been in both Zen and Prb expecting a Zen takeover and an opportunity to buy more Probe and catch it on a takeover premium. It went off in reverse so I've been loading up on Zen this week.
It's likely that that there are majors, their proxies, or corporate speculators buying positions and doing there thing. There always is.
Maybe I benefited this week from the work of whatever player set up the trading bounds and they were willing to give me shares to keep it going. Or, there isn't any risk tolerance to push it out of the range. Either way I'm happy to buy when everyone is sitting on the sideline. Nothing more nefarious then that.
... Been There