Q:

Do curly braces inside json string objects need to be escaped?

This string is part a JSON object/file:
"Mask" : "{0}(CASE WHEN {1} = {2} THEN {3} ELSE 0 END) {4}"

Will JSON recognize that as part of standard JSON notation or do I need to escape those curly braces s somehow?
If so, how does one escape curly braces in JSON?

A:

No. Curly braces do not have to be escaped in JSON.

A:

No, curly braces do not have to be escaped in JSON strings.
JSON is defined in RFC 7159. The Section 7: Strings lists the string characters that must be escaped:

All Unicode characters may be placed within the
     quotation marks, except for the characters that must be escaped:
     quotation mark, reverse solidus, and the control characters (U+0000
     through U+001F).

While all characters can be escaped, curly braces do not have to be.

