Is it not possible to take the RER A from Paris to Cergy St. Christophe? The arena looks like a 21 minute walk from that station. I used to work in Cergy and commuted from the west side of Paris (Étoile) by RER A to Cergy Prefecture several times a week. It was around 35-40 min by RER and I generally didn’t have any issues, but don’t know if things have changed since then.The rental of Accor Arena in Bercy (since it has been remodeled) is such a big blow to ISU and FFSG finances that it has become infeasible. There is no other arena suitable for a GP within Paris intra muros limits. The only one that would be perfect for a GP is Aren'Ice of Cergy-Pontoise north of tje capitale. But it's a real hassle to get there from downtown Paris and worse from main airports. It's so complicated by public transportation that last year for Nationals, it was easier for me to drive up there (a 7 hours trip) than to take a train, the subway and a bus.
It is far from the airports, but you can take one of the other RER lines from CDG or Orly to Châtelet and transfer to the A? That is quite a long trip though.
At any rate, I’m sad IdF isn’t in the Paris area anymore so I have an excuse to visit more often. Bercy was always so convenient, not to mention it was very easy to see skaters at the hotel nearby.