Convert MXF files into CBR TS
Okay thanks to @Mulvya I have found a solution how I can create CBR MPEG-2 TS with stuffing and constant constant bitrate and inside of it VBR VPID. The command for H.264 is: 

$ ffmpeg -i &lt;input&gt; \
-c:v libx264 -x264opts nal-hrd=cbr \
-b:v 30M -minrate:v 30M -maxrate:v 30M -muxrate 35M -bufsize:v 25M \
-c:a aac -ac 2 -b:a 128k \
-f mpegts &lt;output.ts&gt;


This will create 35Mbps CBR TS and inside the TS the bitrate of the VPID will fluctuate a bit around 30Mbps, and also the bitrate of PID 8191 (null PIDs). 
The command for doing the same but with HEVC is the following: 

ffmpeg -i &lt;input&gt; \
-c:v libx265 -b:v 25M -muxrate 30M \
-x265-params strict-cbr=1:vbv-bufsize=25000:vbv-maxrate=25000 \
-c:a aac -ac 2 -b:a 128k \
-f mpegts &lt;output.ts&gt;


Here the TS will be with 30Mbps bitrate and the VPID will be around 25Mbps, this command will create also stuffing (null PIDs) around 5Mbps. Please also note that the bitrate after -x265-params should be in Kbps.