Highly unlikely. MBB is a shared service, so if they were on the same network connected to the same cell then you'd be competing with yourself for bandwidth.
If they were all with different operators there's a chance, but still only a small one, because the higher / variable latency with HSPA services would act to drag all the connections downwards towards the lowest-common-denominator.
You'd first need to establish whether the slow speeds are down to signal or contention at the cell (many users using it).
The first one you can do something about - by experimenting with the positioning of the dongle, upstairs outside normally works best. You may need a USB extension cable to put it outside. For instance I only see 4Meg down with the dongle inside, but 8Meg to 10Meg with it outside.
Alternate option is something like the 3 MiFi device which has two internal antennas to strengthen the signal and it can be out outside the window creating its own WiFi network which you then connect to indoors as long as you're not too far from it.