ERISA's definition of employer security

[Guest Hadden2001]

Under ERISA's definition of employer security, is it possible to have more than one employer's stock constitute employer security?

For example, Company A sponsors a stock bonus plan. Subsequently, Company A enter's into a financial arrangement in which it give Company B options (with no limitations other than the passage of time and value) that will make it A's parent. After this transaction, could both Company's stock be considered employer stock or just that have the parent? This is relevant because the plan is considering selling stock to Company A.

The definition of employer stock in the Code relevant? Notice the different language.