Run a view's bulk operation immediately but in background. Is that possible?
PHP needs something to drive the process, it's not multi-threaded. Drupal's queue process runs by either the client's browser making a series of calls (kind of like it emulates the cron), or by the cron itself. 

Why isn't the cron an acceptable method? You can use something like ultimate_cron The control the schedule for each cron tasks.

Update

As @Molot mentioned, the CLI is an option. I believe shell_exec is subject to PHP's timeout (I could be wrong). See this blog post on executing PHP in an asynchronous fashion.