The initial guard break/pass is missing some of the details necessary to be successful against a killed guard player, but the concept is sound. It's certainly sufficient to deal with an untrained or minimally trained opponent who just instinctively wraps his legs for guard after being taken down.
After the pass, the aikidoka is no longer working against guard. He's in ... I won't call it side mount ... lets say top position on the side against a downed opponent. At this point, his intention is to control and pin his opponent. Classically, this was not done with the opponent's back to the ground as you might see in BJJ/Wrestling/MMA. Instead the objective is to pin the opponent face down where there is less chance of him drawing and using a weapon and his hands can be secured if you are using an arresting technique. I'm not sure whether most Aikidoka normally practice entering into this sort of pin starting with the opponent on a downed position on his back, but I think I may have seen something similar in some related classical jujutsu tradition.
Are these entries as demonstrated workable? Very unlikely against a skilled wrestler/BJJ player/Judoka. An experienced grappler will not feed the energy and arm position that the aikidoka is using to set up the locks. Then again, the same could be said for the standing version of these same moves. No one is likely to feed the standard lunging downward chopping action that many aikido techniques are classically practiced against. In order to apply the techniques in real life, an aikidoka needs a) a lot of skill and b) the understanding of how to adapt the moves to the kind of attacks a real world assailant is likely to use. A sufficiently skilled aikidoka could probably get some variation of those moves against an untrained opponent that he had just taken down.
I'm not sure what the intention of the video was. If the practitioners meant to say, "look at our techniques for beating a killed grappler," then they are out of their league. If they were examining a scenario of "I was throwing my attacker, but I stumbled and went down with him and he instinctively wrapped his legs around me, so here's how I get past that and get back to my original plan of pinning him using aikido until the police show up," then I think they are doing fine.
Many people have debated the street effectiveness of aikido in general, but style-bashing is against MT rules, so I would suggest not getting into that.