I agree that a fission/fusion event is entirely unlikely. Mainly because Pu-238 is not a readily fissionable material (fissile).
However, that being said, the one point that was made in the article is a valid one. If a fission event occurs in a hydrogen rich environment (i.e. liquid hydrogen) than fusion can be supported. The Teller-Ulam device is a 2 stage fusion weapon that uses a fission implosion trigger to initiate fusion in hydrogen rich material (Tritium, Dueterium). The resulting reaction releases a burst of X-rays, heat and pressure. This ultimately causes the (Tritium/Dueterium) to fuse - fusion.
That being said, a fission 'bomb' ignited in hydrogen could initiate fusion.
Fissile material could be fissioned by a simple high power impact. The first fission bombs (Little Boy -Hiroshima) are actually called "Gun-barrel" bombs. They are pretty simple. Fire a fissile projectile (U-235) into another fissile adsorber with enough force and you initiate a fission explosion.
Do that in hydrogen (H1,H2 or H3) and you should start fusion.
If all the conditions were right, it could happen.
I don't know much about the direct fissionability of Pu-238 though. My understanding was that it first needed to adsorb a nuetron, undergo beta decay to become Pu-239 (fissile) then fission after an additional nuetron incident. This is the first time I've heard that it was directly fissionable outside of a neutron flux. Also, the Pu-238 has probably decayed enough by now to have enough impurities in it to make fission all but impossible. Nobody seems to know much about the make-up of Jupiter and the concentration of hydrogen in its atmospere or near the surface.
