Firstly, very good you have the permission to photograph. I have just come back (yesterday) from CDG after spending 8 days there. During those 8 days I was stopped at least 20 times! (Lost count after 20 in fact). It's not the Police that request to see the permission but the Foreign Legion, which are there securing the perimeter. I thought it was the normal army at first but after talking to a few of them it became apparent they were all from different countries, (and having talked to a Brit that explained to me they were on a 3 week rotation at the airport).
Anyway, yes, a car is needed for most runway spots. You also have the parallel taxiways
which are accessible from the T3 train station, right near the Hilton and the Ibis, and adjacent to the Concorde.
Next you have the La Météo
spot, which is great for T1 taxi/stand shots, and if rwy 09R is being used for departures too, as everything using that rwy will taxi past you.
A quick explanation of rwy ops. CDG has 4 parallel rwys, all E/W in direction which makes them only ideal during morning and evening. That's not to say they're impossible during the day but you understand what I mean.
The 2 inner rwys, 27L/09R and 26R/08L are used for departures. The outers, 27R/09L and 26L/08R are used for arrivals. That's true for about 95% of what I saw during my 8 day stay.
Generally AFR (especially heavies), will land on the southern rwy, ie 08L/26R. This being because it's closer to T2 (A-G). Again, when it's hectic they'll be told to land on the northern rwy; there's always exceptions to the "rule". Strangely, the AFR A380 landed on the southern and departed from the northern.
Austral, Seychelles, Madagascar, Etihad, Emirates, Vietnam normally land on the southern. Other longhaul foreign carriers use the northern. Expect SIA A380 to land on the northern and AFR and UAE A380 to land on the southern.
Departures are quite hard to shoot, as the inner rwys are further away from the spots and normally slightly lower due to their distance. Unless 27L is used in the evenings I'd give departures a miss. That's only my opinion however. 09R departures in the evening could also work but the 27s were in use most of the time I was there. In fact only 2 of the 8 days saw the 09s in use.
You have about 3 spots worth mentioning along the northern rwy. The best being by the (bridge) tunnel that comes from the airport itself. Take note however, DO NOT use this tunnel to drive from the terminal, as you can not turn off until several km away! You need to either exit the terminal area via the T2 area and turn left onto the perimeter road, or drive out via Entretien and the Fed Ex cargo area. I would recommend the latter. Turn right as you pass the FDX area, then right again at the next roundabout and onto the motorway. The next roundabout will be another right and that will take you onto yet another motorway where you'll need to exit at the first off-ramp. From there you can just about see the bridge area you need to be at. Just drive up the small incline (you'll have 09L TDZ on your right hand side). Pass over the bridge and take the next immediate right into a lay-by where you can park up!
The other spot along that rwy is further down the same road at another roundabout. In fact it's the next junction you get to. Park up on the verge just after exiting the roundabout. There's a mound there and it's near the 27R TDZ.
Days 4 and 6 are FDX heaven, saturday sees about 10 M1F arriving between 1700-1900!! Add to that the Airbuses too. Last saturday I counted 15 FDX machines in total!
The southern spots I'd recommend would be the 26L TDZ at a place called Z4, near the Concorde memorial. You're a little lower than the bridge area but it's a good spot. You get an unrestricted view of the approach, touchdown and rollout (for about 100m). Good in the early morning and late afternoon. But then you have the problem of which carrier do you want to shoot, as you have the different rwys for different carriers. ie. north and south rwy arrivals. The same goes for the TGV train tunnel spot. This is better for departures though, off 26R. It's through a fence however. All other spots I've mentioned are unrestricted/open.
I generally shot the northern morning arrivals the most as the southern rwys were slightly backlit. But it was nicely backlit so it became a problem for me too, deciding should I do north or south. Having 8 days there made it easier though!
EOS1D4, 7D, 30D, 100-400/4.5-5.6 L IS USM, 70-200/2.8 L IS2 USM, 17-40 f4 L USM, 24-105 f4 L IS USM, 85 f1.8 USM