The above link show a bus from Chislehurst. I only looked at Skinners but you can check diff schools. I think what matters is how reasonable and accessible the commute is. If the commute is straight forward in reasonable time I don't see why not.
There are a few boys who go to Judd from Bromley (mainly Orpington) area. I know of one at Skinners. Travel is easy especially if you live close to the station - 20 mins on the train to Tonbridge.
Distance comes into it for a tied score so if your ds got a score of 415 and the cut off is 415 then others living closer on 415 would get in before your ds. However, the likelihood is that he would get in from the waiting list.
I hope that makes sense.
Most from Bromley area however do look more towards the Dartford/Wilmington schools or Bexley.