The Magic Item Compendium on Appendix 2: Random Treasure makes no mention of Encounter Level and, instead, has the DM determine treasure for each creature present during an encounter individually. On How to Use the Tables, in part, says
Step 1: Roll on Table A–1: Treasure, using the monster’s CR to determine which row you will use.
Step 2: Roll the number of dice indicated and multiply as shown to determine the number of coins.
Step 3: Use Table A–2: Goods to generate each piece using the letter codes provided.…
Step 4: Find the table that lists items of the level or levels in the “Items” column on the table you referred to.… (265)
Thus an enemy's treasure is based entirely on its challenge rating, and the Compendium's treasure distribution by challenge ratings stops at 20. (See also here.) (A foe's equipment is, apparently, still calculated separately; see also here.)
Notes on the Compendium's alternative system
This section's introduction is correct when it says, "It’s now [unlike the Dungeon's Master's Guide's rules] far less likely that you will get hardly any gold, hardly any goods, and hardly any items," but that was true largely only at low levels with the Dungeon Master's Guide's rules. In fact, this DM's experience has been that because the Magic Item Compendium's alternative rules tend to sharply limit the number of magic items per creature—usually to but a lone significant and level-appropriate magic item—, high-level encounters against multiple foes using the Compendium's alternative rules are often less profitable (and, by extension, less difficult) than encounters using original rules from the Dungeon Master's Guide. This DM has bounced between these two systems and has come to respect and prefer the elegance of the Dungeon Master's Guide system despite it being somewhat stingy at low levels.