Level 2 data in the MT L2 Window appears to be incomplete. When running MT and using IB as source for L2 data, it almost exclusively displays NSDQ prices and only displays one MM per price even if there is more than one at the same price. In fact, it may even outright ignore better bids and offers from other MMs or markets.
Say SPY has bids as displayed by TWS:
033 | 204.03 | ARCA
036 | 204.03 | BATS
017 | 204.03 | BYX
072 | 204.03 | DRCTEDGE
017 | 204.03 | EDGEA
017 | 204.03 | NSDQ
036 | 204.03 | NSDQ
111 | 204.02 | ARCA
095 | 204.02 | BATS
024 | 204.02 | NSDQ
096 | 204.02 | NSDQ
454 | 204.01 | ARCA
125 | 204.01 | BATS
036 | 204.01 | NSDQ
096 | 204.01 | NSDQ
and offers
008 | 204.04 | ARCA
134 | 204.05 | ARCA
025 | 204.05 | BATS
004 | 204.05 | BYX
027 | 204.05 | DRCTEDGE
004 | 204.05 | EDGEA
004 | 204.05 | NSDQ
074 | 204.05 | NSDQ
507 | 204.06 | ARCA
096 | 204.06 | BATS
001 | 204.06 | NSDQ
169 | 204.06 | NSDQ
then MT displays
040 | 204.03 | NSDQ
096 | 204.02 | NSDQ
122 | 204.01 | NSDQ
and
078 | 204.05 | NSDQ
074 | 204.05 | NSDQ
169 | 204.06 | NSDQ
Note that MT ignored the 204.04 offer on ARCA completely and that some of the sizes for NDSQ also don't match with what TWS displays. From time to time I could also see UBS and Timber Hill quotes but for the most part MT was exclusively displaying NSDQ. As an additional note: I was also connected to IQFeed but I don't have L2 there and specifically selected IB as a data source because of this.
MT Version: 1.0.5947.932