It's complicated because Bloomberg, Reuters and the Financial Times are usually top-level economic data companies that many banks themselves will source data from, but these media companies will in-turn source their data from the banks. Other sources include the central banks, brokers, IMF, statistics companies, investment mangagement firms, investors, companies that deal in large amounts of FX, etc... basically anyone who is considered by the media company to be affecting FX rates.

The top three that I listed above certainly have similar levels of access to financial data for live FX rates, but technically media companies will compete to provide the best FX rates possible so obviously there will be differences between companies.