Which call routing pattern is used for phone numbers that are in the E.164 format?

The forward slash / is not the correct escape character for the plus sign in CUCM route patterns; a backslash \ is required.

The \+.! route pattern is the correct wild-card representation for matching E.164 numbers. The backslash escapes the plus sign, indicating it is a literal plus, and the . (dot) matches any single digit, while ! (exclamation mark) matches one or more occurrences of the preceding character (the dot), effectively matching a plus sign followed by one or more digits.

While \+.! can be used in a translation pattern, the question asks for a 'call routing pattern'. A route pattern is directly used for routing calls, whereas a translation pattern is used to modify digits before routing. For E.164 routing, a route pattern is the primary mechanism.

This is a specific pattern for North American Numbering Plan (NANP) numbers, not a general pattern for all E.164 numbers. Also, it specifies a 'called Party Transformation pattern,' which is for digit manipulation, not the primary routing pattern itself.