The antibacterial spectrum of fosfomycin includes staphylococci, Haemophilus sp. and most of the enteric gram-negative bacteria, but with a considerably higher MIC for Klebsiella sp., Enterobacter sp. and Serratia sp. Fosfomycin is moderately active against Pseudomonas aeruginosa with variable MICs ranging from 4 to >512 mg/L.

PO fosfomycin is not effective against Pseudomonas. In case of sensibility, IV is efficaceous and could be used. 

In Russian insert fosfomycin is mentioned as particularly suitable to treat Peudomonas aeruginosa infection - but I would first test the strain in queestion against  fosfomycine

Though fosfomycin may be a good alternative to treat Pseudomonas infection but is dangerous to use it in UTI as it can impair the function of the kidney significantly.

The only PO drug that can be used to treat Pseudomonas UTI is Ciprofloxacin if pseudomonas is sensible. Fosfomycin high dose IV to treat Pseudomonas UTI should be restricted to cases the microorganism is sensible and there are no alternatives and should always be combined with fast bactericidal antibiotics like aminoglucosid 

Fosfomycin is specifically active against E cli and Staph aureus including MRSA. It has a considerable effect on pseudomonas, although i would not advise using it for such suspected pathogen unless proved to be effective by culture and sensitivity study. It is effective orally and its effect starts within 4 hours. For suspected pseudomonas infection, i would advise either fluoroquinolones or the combination of B lactam antibiotic with an aminoglycoside.

Pseudomonas has variable susceptibility to Fosfomycin. If the pseudomonas carries FosA resistant gene then using Fosfomycin will be ineffective. If Pesudomonas does not have Fos A resistant genes, then yes it can be used to treat acute uncomplicated cystitis.