Judgment on construction power supply - assessments / experiences?

Nope. The professional has to approve the scaffolding in the end; anyone can build it. Please don’t tell me that the "scaffolders" you find on large construction sites and increasingly also at single-family house constructions, whose language you don’t understand, are all trained scaffolders. And even among the German crews, there are always helpers who are just semi-skilled.
It’s like with electricity. A layperson can also install and connect it entirely on their own, as long as in the end the master electrician does the measurements and signs the protocol.
You just have to find someone who signs it. That shouldn’t be a problem within your circle of acquaintances.

And even then, the professional does not always take responsibility if someone falls. It’s like with car inspections. The inspector signs off on the condition he checked on day x. What happens three days later because someone tampered with it is no longer the inspector’s problem.
In our case, the bricklayers already removed several scaffold planks or just placed them loosely somewhere after two days because it was easier for them to reach. Then no scaffolding master is liable if the bricklayer falls two floors down.

Then we can safely heat the screed with construction electricity for 48 cents. I was already thinking of renting a trailer with heating oil

How do you come to that? The contractor has to take care of the construction electricity. Specifically, the ruling refers to the common practice of blaming the client for the construction electricity and then saying "No construction electricity? Then we can't start and the fixed price is at risk because you are not delivering your services on time."

The ruling does not automatically mean that the contractor has to cover the electricity costs. Especially since there is no automatism behind it. Although there is now a precedent, every client still has to sue individually at the moment.

Or first point out the matter and see how the BU behaves... At least I see the connection fee on the part of the BU

There is an article in Handelsblatt titled "Construction water and construction power do not come from the client" which can be found on Google.
Existing clauses are also invalid.
In your opinion, should the also be paid by the construction company or only the consumption?

Or first point out the circumstances and see how the contractor behaves...
At least I see the connection fee on the part of the contractor

A Bavarian contractor can sit back extremely relaxed in view of a ruling by a Northern German Higher Regional Court, even if it cites the Building Code in its reasoning. More than inspiring your responsible local judge, this ruling initially does not amount to anything. Moreover, the case dealt with a defect where the contractor argued that he was prevented from delivering a defect-free service because a power connection was required for proper performance and its provision was the client's responsibility. The court rejected this and cited the nullity of this obligation as its reasoning. The consumer law question of who should bear which costs was not even litigated. The contractor’s general terms and conditions were therefore not even challenged here.

In your case, it would first depend on the subject matter of your claim; as mentioned, the local judge does not have to care about the ruling from the North at all, and if, for example, you were to complain about the passing on of costs to you, only the contract between you and your construction company would be relevant. If the local judge’s assessment of everyday reality is the same as mine, it would even be the other way around: accordingly, the connection costs would rather be regarded as an included service than the consumption (but as said, if your contract is valid: if it imposes the construction power on you, then you would have to pay for both parts).

Can you try, it doesn't cost anything. But you should expect that heating will initially not be provided for 48 cents/kWh if you ask your [BU] to cover the electricity costs.