It might be difficult to say whether the speaker is mocking or praising the absent mother's effort because the speaker throws in some sarcastic lines such as suggesting the plant was oiled rather than watered, or that the cans are like sirens calling out to the cars:
arranges the rows of cans
so that they softly say:
Despite the sarcasm and the detailed criticism throughout the majority of the poem, the speaker does respect the fact that somebody cared to water the plant, embroider the doily, and do other thoughtful things to at least give the impression that an effort was made. In other words, the proof is there that someone cared enough to make the effort.
Notice the SO-SO-SO alliterative continuation of the second syllable of ESSO. The alliteration continues/was continuing the SO that begins the word "SOmebody." Despite all the dirt, somebody made an effort and the speaker clearly noticed it. Obviously, the SO of ESSO is not there to imply that somebody cares, but the speaker adds that meaning and this could indicate that she (speaker) appreciates the care taken to arrange the cans.
Even if the speaker thinks it was a waste of time to try and class up the station, it was not a waste of time because that effort at least caused the speaker to consider how she, and other people, are likewise watched and possibly loved as well. The fact that she used "us" rather than "them" in the last line illustrates this point that the mother's thoughtfulness towards her family caused the speaker to consider how similar thoughtfulness and effort might exist in her own life.