Regarding what may happen, the worse conceivable outcome is being forced to turn back, especially on your way out. But I assume that even if there is a border check, it would most likely be possible to talk your way out of it.
I am not sure for Switzerland but a fine is not a risk in France, you are supposed to have an official form of ID to cross the border but it’s not an offense not to have one within the country. So even if, formally, your attestation is not enough (and it might be for all I know), there is no legal basis to impose a fine or anything. The police could retain you for some time to ascertain your status but with so much evidence of who you are, the fact you are an EU citizen and actually work for a French diplomatic mission, it would just be a waste of time for them (you have a right to be there regardless of any documentary issue and there is no way on earth it would end up in a forcible removal).
Also, my personal experience with this border (which I have had many occasions to cross over the years) is that things are more-or-less back to normal there. A spot check is always possible but when police is present (which it isn’t, most of the time), they usually just look at you and wave you through without asking any question. The only place where I have seen systematic document checks is when boarding French trains at Geneva train station.
According to this, you can enter Switzerland with your German ID or Passport even if they are expired. If you don’t have the expired ones… Well – that’s bad.
Alle Reisedokumente außer dem vorläufigen Personalausweis dürfen auch seit einem Jahr abgelaufen sein. Es kann jedoch vorkommen, dass die Rechtslage in Bezug auf die Nutzung abgelaufener Reisedokumente nicht überall bekannt ist. Daher wird empfohlen, gültige Reisedokumente mit sich zu führen.
For non-german speaking: it says your ID’s can be expired (with a maximum of 1 year), but it’s not recommended to use those, as this change is recent and not known to everyone.
As for France – this says as well that your ID can be expired (max 1 year due).
Reisedokumente außer dem vorläufigen Personalausweis dürfen seit höchstens einem Jahr abgelaufen sein.
States basically the same thing, just without the warning.
Yes, in practice you can easily cross the border between Switzerland and France as both are in the Schengen zone and under normal circumstances, there are no border checks between them. You can literally just walk across the border in many areas and there is nobody to check. I’ve done it many times, with or without ID. If you don’t pay attention you might even cross without noticing.
Col de Balme at the border between Switzerland and France. Source: Wikimedia Commons.
Of course, different countries still have de jure requirements about carrying IDs, either at all times or when crossing a border, but it is up to you whether you choose to meet those requirements in practice.
Credit:stackoverflow.com‘