Let's face it, none of the 40k authors are even aware of the role of lances in BFG. They just look for a "precise" weapon to use in their fluff. Since some of the lance wielding SM fluff predates BFG then perhaps the way lances operate in-game should have been changed, such that they're accurate against stationary targets like WBs, etc.
However, since they weren't made that way, and the way they did function was as pure anti-ship weapons, the SM fleet was designed with an alternative. Moreover, fluff was added to stipulate that SMs should not get lances on their ships. This makes sense, as they're not meant to be a warfleet.
40k fiction lance = precise orbital bombardment
BFG game lance = anti-ship weapon
The similarity of name should not confound the desire for the first in fiction with the acceptance of the second in game. Now, we know that laser batteries are used as WBs. Presumably they be used for precision strikes (despite attenuation for atmosphere). As for the nomenclature used in fiction describing lance attacks by SMs, well that can be rationalised to say reflect the type of attack rather than type of weapon. Ie, when precision is called for, they call for a lance strike (focussed rather than area saturation). On the scale of BFG, a lance strike means something else, and so specialised weaponry and targeting systems are called for.
I don't say all this to reopen the debate. Obviously those SM, er, "fans" that want lances on SM ships will still want them. They'll likely find the above unconvincing. However, it does mean that no amount of incidental 40k fiction using the word "lance" will impact on the game rules of BFG. Does that mean that fiction is not counted as evidence? No, it means that for it to be counted as evidence it would have to first account for all the fiction. This includes the stipulation against SM warships and the Nova fluff. There would also have to be a perceived need for them, to justify the trouble. Given that SMs have precise orbital strikes with their WBs (read lasers) and have bombardment cannon *I* can't see this happening. It seems to me that this would be lances for the sake of lances. Of course, again, those that want them wouldn't find my opinion of any value. It's like the existence of God. Arguments for or against are unconvincing for those not of like mind.
So, the real point of this post is to highlight what is required for a convincing argument. That is: fiction showing SMs with lances which accounts for previous attitudes (no SM warships, which lances equate to); and a clear need. To my knowledge the first doesn't presently exist and the second is not currently exigent either. Perhaps some new race will pop up that has fast nimble warships with high armour that the IN can't deal with ...