[hippich]

From what I know about i2p - there is no gateways to "outside" internet. As a result, this will work only with other i2p bitcoin clients, correct?

[synchronise]

There are fewer gateways than Tor, but it will connect to the internet and function normally.

[Tmmrn]

By the way, "outproxy" is the word for them. (In case others don't know)

[gasull]

Nodes can share the same blockchain within the I2P network and to the open Internet. If enough nodes do this, then the resulting blockchain will be the same in both networks.