Deutsche Bahn: Do I need to buy and later claim a refund for using a different train due to a cancellation or delay in the original train?

Question

Suppose I have booked a train with Deutsche Bahn from A to C via B. Either the train covering the A-B leg gets delayed, or the train covering the B-C leg gets cancelled, leaving me looking for alternative options to get from B to C. This answer says that in such a scenario, I could take any subsequent train that goes from B to C, without having to buy a new ticket.

However, according to the Deutsche Bahn web page on passengers' rights (emphasis mine):

If the train is expected to arrive at the destination with a delay of at least 20 minutes, you can:

• continue the journey at the next opportunity or at a later time on the same or a different route
• use a different train for which no reservation is compulsory (you are obliged to pay additionally required tickets/supplements, but you can subsequently claim for a refund of these costs). The foregoing regulation does not apply to tickets for a substantially reduced fare (e.g. regional day ticket (original name: Länder-Tickets), weekend ticket for Germany (original name: Schönes-Wochenende-Ticket).

My questions are:

1. Does this mean that I would need to buy a new ticket and later claim a refund? I am specifically interested in the case of Super Sparpreis tickets, since this issue would not arise with Flexpreis tickets.
2. Does the answer change if my original ticket was with a regional train? If so, am I allowed to take any subsequent train, even if it is an IC/ICE, or must I stick to subsequent regional trains? What if the regional train was a part of a larger reservation that included a long distance leg with an IC/ICE?

Answer 1

Buying a new ticket/supplement is for one necessary, if you want to use a train with compulsory seat reservations.
Example with a ticket A-B-C: If you miss the last ICE from B-C because the train A-B was delayed, and the only remaining possible train would be a Nightjet, you can use it, but you would have to pay the supplement first, and later reclaim it, since Nightjets have mandatory reservation.

Another usecase, as i mentioned in the comment on the other answer, if you have a ticket only for regional trains, and you want to use an ICE, then you also have to buy the ICE ticket and reclaim the costs.
Note: this applies only if the whole ticket itself is only valid for regional trains. If you have a ticket A-B-C where A-B is on an ICE, B-C would be a regional train, and you want to use an IC or ICE for B-C, because the first ICE was delayed, you don't have to buy an additional ticket for B-C, since your ticket is already an ICE ticket.

So regarding question 2, if you have a long distance leg on your ticket, you don't have to buy any new tickets, if you want to take IC/ICEs on originally booked regional train parts, if previous trains were delayed.

Answer 2

The german version of the DB website gives some more details:

Wenn Sie eine Fahrkarte des Nahverkehrs (RE, RB, IRE und S-Bahn) besitzen, aber einen höherwertigen Zug (z.B. Züge des Fernverkehrs, also IC/EC, ICE) nutzen möchten, dann müssen Sie zunächst die zusätzlich erforderliche Fahrkarte bezahlen. Anschließend können Sie die Kosten [...] zurückfordern

Rough translation: If you have a ticket for a regional train (RE, RB, IRE, S-Bahn), but want to use a higher-class train (e.g. long distance trains, IC/EC, ICE), you have to buy the necessary ticket / upgrade at first. Later you can reclaim the cost.

So for the kind of journey you mentioned at the beginning of your question (journey with two legs), it doesn't depend on the kind of ticket you have, but on the kind of train you were supposed to take from B to C:

• If you have a ticket for a long distance train going from B to C, you can just take the next available train and don't have to buy a new ticket. This also includes "downgrading" - sometimes taking a regional train is faster than waiting for the next long distance train.
• If you have a ticket for a regional train going from B to C, you have to buy a ticket for a long distance train first and claim the refund later.

Unfortunately, I have no idea about the second case of your number 2 (journey with more than two legs).