Will it be possible to provide short term power to the B2+ model with the following setup?
Will the micro-USB power adapter work for the pi?
I ended up getting a slightly different model which is directly pluggable into the socket, includes the rechargeable battery. Everything works fine in combination with the listed coaxial to micro-USB adaptor.
Yet, the question was not about specific products, it was more about a certain class of configuration, so the technical wording of the question would be Is it possible to power the PI with a mini UPS which is not built specifically for the PI and has a different power plug. Searching for mini UPS was what led me on the right track.
The answer is yes, it works with the given combination, and in unplugged state I get roughly 90 minutes of continuous MP3 playback with a connected 32GB USB flash stick.