Use the Cadence Allegro Viewer after converting the .asc file to .brd file.
Follow these steps to convert the .asc file to .brd file:
1. From the Cadence Allegro Viewer, click Import -> CAD translators -> PADS.
2. Select the .asc file that is available in the BGA breakout and routing folder as input.
3. Provide a name for saving the .brd file.
This file can be opened with Cadence Allegro Viewer.