Not that I'm aware of.
One thing you may or may not know is the desert in vanilla has actually 3 biomes in it.
You have 1 main biome and 2 additional sub biomes.
1 thing you can do as a test is change the surface layer terrain of one of the sub biomes in the desert to a different terrain.
Code:
<layers>
<layer depth="1" blockname="[color="#FFFF00"]desertGround[/color]" />
<layer depth="22" blockname="sandStone" />
<layer depth="*" blockname="sandStone" >
<resource blockname="leadOre" cluster="1" prob="0.1030" rwgGenerationType="all" />
<resource blockname="oilDeposit" cluster="1" prob="0.1130" rwgGenerationType="all" />
</layer>
<layer depth="3" blockname="bedrock" />
</layers>
change one to burnt terrain blocks to see how it lays them out.
Then insert your coal into that biome.
Code:
<layers>
<layer depth="1" blockname="[color="#FFFF00"]burntForestGround[/color]" />
<layer depth="5" blockname="sandStone" />
<resource blockname="[color="#FFFF00"]gravelPlusCoal[/color]" cluster="1" prob="[color="#FFFF00"]0.1[/color]" rwgGenerationType="all" />
</layer>
<layer depth="17" blockname="sandStone" />
<layer depth="*" blockname="sandStone" >
<resource blockname="leadOre" cluster="1" prob="0.1030" rwgGenerationType="all" />
<resource blockname="oilDeposit" cluster="1" prob="0.1130" rwgGenerationType="all" />
</layer>
<layer depth="3" blockname="bedrock" />
</layers>
Setting it up like the above ^ you should see a section of the desert that has patches of burnt ground with gravel patches. dig 1 layer down in those gravel patches and you should see patches of coal here and there with a chance on every layer for 5 layers down.
edit: with the way I set it up you may or may not see those gravel patches but just dig 1 layer down and spawn in an auger you should start hitting coal.