Currency trades will be performed within the integrated DEX (3rd party exchanges are supported also, but have no impact on the economics), with tokens representing other world currencies. These tokens are pegged to the respective currency and can be converted to actual fiat currency via a network of on/off ramps through another system component called TRAID.
Initially the buffer will hold only EMU, users will "buy in" with USD tokens, that they can then trade on the DEX for EMU. This is the basic mechanism with which the buffers obtain other asset types.
These tokens can also be used to buy goods/services if the merchant wishes to accept them. World currency tokens can not be traded freely in the DEX, 1 USD token is worth 1 real USD.
The system must maintain a chain wide majority holdings of EMU for this to be effective, and also be fortunate enough that the initial sell off of EMU for USD tokens does not then lead to a situation where the system is not a chain wide majority holder of USD tokens.
Obviously there is counterparty risk associated with the (multiple?) gateways... Will each gateway have its own USD token? If not, how do you get them to agree on the value?