1) Broker Dealer
2) Be a market maker
3) JBO
Also cross margin is limited to OCC' eligible products list:
http://www.optionsclearing.com/risk-management/margins/cross-margin-eligible.jsp
http://www.optionsclearing.com/risk-management/margins/cross-margins.jsp
Participation
Cross margining was designed for firms with memberships across various clearing organizations which guarantee products that are highly correlated. Due to differences in securities and futures related customer protection requirements, the program is only open to clearing members and their affiliates, and market professionals who include market makers and futures locals.
In order to facilitate the cross-margin process, participating clearinghouses establish joint clearing accounts for each member. In the event of a default, the clearinghouses' arrangement provides for the treatment of all assets and obligations associated with the cross-margin account as well as the other clearing accounts of the defaulting member.
Margins
Clearing level margins are computed based on the combined positions maintained in the cross-margin accounts using OCC's proprietary System for Theoretical Analysis and Numerical Simulations (STANS). STANS is a portfolio-based margin methodology that utilizes a sophisticated options pricing model to identify the economic risk inherent in a portfolio. By combining hedged positions cleared at separate clearinghouses into a single portfolio for margin and settlement purposes, the real risk of that portfolio can be determined. This results in a more appropriate margin requirement, which is typically lower than if margins were calculated separately. The average daily margin savings realized by firms participating in cross margining have been significant.
Operational
Cross margin trades are executed on the exchanges for which the participants clearing organization clear trades and typically are transferred to a joint account via Clearing Member Trade Agreement (CMTA) or give-ups. At the end of each trading day, the futures clearinghouses transmit closing positions and settlement activity to OCC, which in turn calculates clearing level margining and then produces and distributes position, margin and settlement reports to clearing members.
Summary
Cross margining has proven to be a viable tool for participating firms, allowing them to enhance the efficiency and the ability in meeting their financial obligations to the marketplace. This is especially important during periods of increasing market volatility. By recognizing intermarket hedged positions cleared by different clearing organizations, cross margining increases the overall efficiency of the clearing and settlement process, providing reduced initial margin requirements as well as increased liquidity in the form of net settlements.