Can I take a bicycle with me on DB-ÖBB services passing through the Brenner Pass?

Yes, with a long-distance transport bicycle ticket and a bicycle space reservation.

On DB-ÖBB trains between Munich and northern Italy (Verona/Venice/Bologna), folding bikes can be taken on board when folded, provided they do not exceed the dimensions of 90 x 60 x 40 cm. The folding bike must be stowed above or below the seat or in the available luggage racks. Each passenger is responsible for their own luggage.

You cannot take packaged and (partially) disassembled bicycles with you on the train.