I don't think that this move will improve WBOQ's signal in Boston proper or in the south suburbs. It will noticeably improve their coverage in the Merrimack Valley, metro north and northwest, and southeastern, south central, and coastal NH. Lawrence will now be within their primary contour, which wasn't before. Lowell will get a much improved signal. Areas along Route 495 north of the Pike will get a somewhat stronger signal.
I predict that the signal in Boston proper and heading down the Route 95 corridor south (toward RI) will actually be a bit weaker than it is now for two reasons:
#1: Despite the overall increase in power, the signal from Topsfield will no longer be coming mostly over water toward Boston as it had from Manchester-By-The-Sea. I know that salt water conductivity is mainly only a factor for AM radio, but the difference for FM will be that from Manchester toward Boston it was mostly open terrain over water with practically no obstructions for the FM signal. The new location from Topsfield will be coming toward Boston all over land (the Route 1 corridor), with hills and various other terrain factors between there and Boston that won't allow as nearly unobstructed coverage as it had over water. This may also diminish their coverage of the South Shore somewhat, which used to be directly over water from Manchester.
#2: In order to increase their wattage in all other directions, their soft null to the south/southwest of their transmitter, toward Boston (and beyond toward RI), appears to have to be more pronounced than it was previously to protect WWLI (and perhaps WOCN on the Cape). It looks like Boston and toward Route 95 south, and the South Shore, will actually receive a bit less signal strength from WBOQ than it did before.
I don't believe that this increase for WBOQ will cause any more of a problem for WRBB than their present signal in the Boston area already does, and former WODS oldies fans who, from the hype from WBOQ, are expecting a strong analog replacement for the old WODS Classic Hits format in the immediate Boston metro (and to the south) are going to be very disappointed. I'm not going to try to explain this to all the hopeful former WODS listeners on WBOQ's Facebook page, let them find out for themselves and express their disappointment.