Yes, this is possible, if you can get the packaging system of your UNIX operating system to install both syslog-ng and syslogd at the same time. The syslog-ng application can be configured not to process locally generated messages, and local syslogd can be configured to send all log messages to syslog-ng using the UDP protocol using the following configuration line:

 *.*                       @127.0.0.1

Please note that syslogd might open the syslog UDP port automatically, in which case the above configuration will cause all syslog messages to be resent to itself, causing an endless loop.

The syslog-ng application can accept messages from syslogd using the ''udp()'' source.

One can also use a named pipe to send logs to syslog-ng. From man syslogd:

 This  version  of  syslogd(8) has support for logging output  to named pipes (fifos).  A fifo or named pipe can be used as a
 destination for log messages by prepending a pipe symbol ("|") to the name of the file.   This  is  handy  for  debugging.
 Note that the fifo must be created with the mkfifo(1) command  before syslogd(8) is started.