custom bbcode that implies a [plain] block?

I'd like to have a custom bbcode which has the same effects as and wraps stuff in HTML tags. (Specifically <tt>, for inline code samples as opposed to code blocks.)

I can do <tt>{text}</tt>, but bbcode in {text} is still parsed. If I put [plain]{text}, the plain tags show up and the other tags are still parsed. Can this be done without a PHP callback?