How to link to dblog filtered by type?
It is possible, but the values used to filter that list are put in $_SESSION['dblog_overview_filter']. Linking to that page and making it shows the messages filtered by type is only possible if you set that session variable with the right value. Looking at the code of dblog_filters(), I get that the following line would cause that list to show the logs about cron tasks.

$_SESSION['dblog_overview_filter']['type'] = array('cron');


References


dblog_overview()
dblog_filter_form()
dblog_filters()