Can I swap TX+ and TX- (and RX+ and RX- ) using ethernet magnetics?
As long as the RJ45 connector line pinout adheres to the standard, you shouldn't have any problems. The magnetics are a passive device, they don't care about RX + or RX-.

You can even get away with RX/TX crossing on the connector side, as most modern NICs and switches have auto MDI/MDI-X capability.
Some PHYs allow you to set the transmission polarity in their configuration, but I wouldn't rely on that capability.