[aselzer]

Of course they interfere, Bluetooth and Bluetooth LE use the 2.4-2.48 ISM band, and so does WiFi. WiFi has up to 14 overlapping 20MHz channels, and Bluetooth 4.0 has 40 2MHz channels. Though I guess Bluetooth could be clever enough to avoid the channels with interference.

[IneffablePigeon]

BLE has 3 advertising channels, spaced to try to avoid the WiFi channels. Once a connection is made (probably not relevant for beacons anyway), it uses frequency hopping over the other 37 channels to avoid interference as much as possible.