ME p2p tunnels are essentially used to move channels from an interface to another location. There are also other P2P Tunnels such as Light, Redstone and these work much the same allowing you to move fluids, Redstone and light from one location to another via your ME network.
Who needs expensive cables or pipes when you can use ME Cables.
Remember these tunnels may seem like a good idea but they do cost channels!
Light tunnels allow you to move light from a glowstone block or a torch to another location, these are not used very often as they require channels to function.
RF p2p tunnels can have cables go straight into them and have this power come out the other end, instead of using expensive RF cables we can carry RF over the AE system. Please bear in mind that if you input 512 RF/t you will also export 512RF/t, you can add more tunnel's but serenely these tunnels have unlimited bandwidth but they have about 5% tax on your input amount. The EU variation of the cable will work in the same way but will only accept EU.
The blow example used 3 redstone P2P tunnels, one input with a Level that is turned on and 2 outputs with redstone lamps in front of them, instead of running redstone to each lamp the ME system is carrying the redstone signal and sending it ot any tunnel I need with no limits on its range: