As far as I can tell from the website, the t+ ticket doesn't allow transfer between RER and tram (https://www.ratp.fr/en/titres-et-tarifs/t-tickets). Is there one that does, or do I need two tickets? I'm traveling from Gare du Nord to Pont de Bezons
If you use the quickest itinerary (RER B or D to Châtelet-les-Halles, RER A to La Défense, tram 2), you need two separate tickets: one from Paris to La Défense, and one for the tram. The ticket from Paris to La Défense is a point-to-point ticket (currently costing 2.80€). For the tram, it's an interchangeable ticket t+ (one for 1.90€, 10 for 14.90€).
You can use a ticket t+ for either of these possibilities, but not both with the same ticket:
- Anywhere in the metro, plus RER within the Paris city limits (zone 1 on maps). Note that La Défense is not within the Paris city limits, so a ticket t+ is valid for La Défense using metro line 1 but not using the faster RER A.
- Anywhere in the bus and tram network within the Île-de-France region. Some longer bus trips and night buses require multiple tickets for a single journey.
A point-to-point ticket whose endpoint is Paris allows traveling with the metro and RER within Paris consecutive to the train journey (before or after, depending on whether you're traveling from or to Paris), but not with the bus.
A point-to-point ticket can also have a station on part of tram T2 (La Défense–Issy-Val-de-Seine) as one of its endpoints, for historical reasons (it's a former train line). But Pont de Bezons isn't on this section.
There's a plan to introduce fully combined ticketing but as of June 2019 it still hasn't been carried out.
You can get there with a single ticket t+ (itinerary with bus+tram only) if you want to save money, but the journey will take about twice the time (35 min vs 70 min). You can also take a train to La Garenne-Colombes, Houilles-Carrières or Val d'Argenteuil (with a point-to-point ticket ending in that station) but you may have to walk a lot more depending on where exactly you're going.