This is a very important question that we have no good answer for right now. Presumably, if a star looses more than 1/2 its mass, any orbiting planets will become unbound. It seems that the progenitor star for the pulsar in question only lost les than 1/2 its mass so the planets could survive in highly elliptical orbits. Presumably, over time, these orbits can become circular by the emission of gravitational radiation, or tidal dissipation processes. But we just don't know for certain.