City ticket included for German IC trains validity

Yes, because "tarifliche Gleichstellung" (station grouping) applies. In such a case, you get a ticket that does not have the name of a specific station as start or endpoint, but the name of a station group. You can see that this applies to your case because the startpoint is listed as "Bremen" (the name of a station group) instead of "Bremen Hbf" (the name of a specific station). So you can start your trip at all stations in the station group of Bremen, which you can find on page 7 and 8 of this list in the second-to-last column. In the case of Bremen, the station group goes as far north as Bremen-Farge.

Explained differently, station grouping means that for long-distance tickets (> 100km) all stations in certain sets of stations are treated as if they were identical. The regulations for station groups are in this PDF in Section 3.7.

As mentioned by Tor-Einar, the City-Ticket option often also allows traveling to your startpoint. There are some important differences though:

• City-Ticket is valid for all public transport, with station grouping you must use trains only.
• City-Ticket is not included in super saving fares (Super Sparpreis), station grouping is.
• City-Ticket is available only in about 130 cities, station grouping also exists in many other smaller cities and towns, some of which have only a few thousand inhabitants.
• The covered area can be different. City-Ticket is usually valid in some specific zones of local public transport (current list), whereas for station grouping a different list of stations applies.
• City-Ticket is indicated by the explicit "+City" marker, station grouping is visible through the use of a name of a station group. However, the latter can be difficult to notice because there exists cases where the name of a station group is the same as the name of an existing station (e.g., "Hamburg-Harburg"), in which case you would need to check the trip distance to find out whether station grouping applies to your ticket.