Hi Jake! BLE (aka Bluetooth 4.0) is not the same kind of Bluetooth you would use to talk over a car stereo (suggested reading: https://tessel.io/blog/94173952967/you-probably-dont-need-an-ibeacon). So, although we have a BLE module, I don't think anyone has tried using a Bluetooth Classic connection through Tessel 2.
Just reread your question, and I'm not sure if I'm answering what you asked. It seems like this might be the more straightforward question of whether an iPhone can support multiple peripherals– I would expect yes. I use Android, but I can have my Pebble (BLE) connected at the same time as my motorcycle helmet's headset (Bluetooth Classic).