Not owning a car, that's something I've only thought about superficially, but most recumbents are, by nature, a single rigid pole with stuff attached, which is going to be significantly more awkward to fit in a car than an upright (which tend to have useful bendy bits and removable wheels that change the overall length). If it works at all, it's going to be either with the aid of a big car, or some time-consuming spanner work.
I can't imagine the majority of bike carriers are very recumbent-friendly, either. Roof-mounted is likely to be the best approach.
There's a lot to be said for folding, in this context. The nifty fold of the newer Trices, while perhaps suboptimal for trains, is clearly a massive win for sticking-it-in-the-back-of-a-car purposes.
